Methods of synthesizing an oxidant and applications thereof

ABSTRACT

Novel methods and devices for synthesizing ferrate and uses thereof are described. One aspect of the invention relates to synthesizing ferrate at a site proximal to the site of use, another aspect of the invention relates to devices and methods for synthesizing ferrate.

RELATED APPLICATIONS

The present application is a continuation-in-part of the U.S.application Ser. No. 09/905,165, filed Jul. 12, 2001, now abandoned, byCiampi, and entitled “METHODS OF SYNTHESIZING AN OXIDANT ANDAPPLICATIONS,” which in turn claims priority to U.S. ProvisionalApplication Serial No. 60/218,409, filed Jul. 14, 2000, by Ciampi, andentitled “METHOD AND SYSTEM FOR TREATING WATER AND SLUDGE WITH FERRATE,”and U.S. Provisional Application Serial No. 60/299,884, filed Jun. 21,2001, by Ciampi, and entitled “METHODS OF SYNTHESIZING AN OXIDANT ANDAPPLICATIONS,” all of which are incorporated by reference herein intheir entirety, including any drawings.

FIELD OF THE INVENTION

The present invention relates, generally, to the manufacture and theapplication of the ferrate ion. More particularly, the present inventionrelates to methods and systems for treating, with the ferrate ion,solutions containing impurities.

BACKGROUND OF THE INVENTION

The ferrate ion, FeO₄ ²⁻, is a tetrahedral ion that is believed to beisostructural with chromate, CrO₄ ²⁻, and permanganate, MnO₄ ⁻. Theferrate ion has been suggested to exist in aqueous media as thetetrahedral species FeO₄ ²⁻. Redox potentials for FeO₄ ² ion have beenestimated in both acidic and basic media (R. H. Wood, J. Am. Chem. Soc.,Vol. 80, p. 2038-2041 (1957)):

FeO₄ ²⁻+8H⁺+3e ⁻→Fe³⁺+4H₂O E°=2.20V

FeO₄ ²⁻+4H₂O+3e ⁻→Fe³⁺+8OH⁻E°=0.72V

Ferrate is a strong oxidant that can react with a variety of inorganicor organic reducing agents and substrates (R. L. Bartzatt, J. Carr,Trans. Met. Chem., Vol. 11 (11), pp. 414-416 (1986); T. J. Audette, J.Quail, and P. Smith, J. Tetr. Lett., Vol. 2, pp. 279-282 (1971); D.Darling, V. Kumari, and J. BeMiller, J. Tetr. Lett., Vol. 40, p. 4143(1972); and R. K. Murmann and H. J. Goff, J. Am. Chem. Soc., Vol. 93, p.6058-6065 (1971)). It can, therefore, act as a selective oxidant forsynthetic organic studies and is capable of oxidizing/removing a varietyof organic and inorganic compounds from, and of destroying manycontaminants in, aqueous and non-aqueous media.

In the absence of a more suitable reductant, ferrate will react withwater to form ferric ion and molecular oxygen according to the followingequation (J. Gump, W. Wagner, and E. Hart, Anal. Chem., Vol. 24.,p.1497-1498 (1952)).

4FeO₄ ²⁻+10H₂O→4Fe³⁺+20OH⁻+3O₂

This reaction is of particular interest to water treatment because itprovides a suitable mechanism for self-removal of ferrate from solution.In all oxidation reactions, the final iron product is the non-toxicferric ion which forms hydroxide oligomers. Eventually flocculation andsettling occur which remove suspended particulate matter.

The use of ferrate may therefore provide a safe, convenient, versatileand cost effective alternative to current approaches for water,wastewater, and sludge treatment. In this regard, ferrate is anenvironmentally friendly oxidant that represents a viable substitute forother oxidants, particularly chromate and chlorine, which are ofenvironmental concern. Ferric oxide, typically known as rust, is theiron product of oxidation by ferrate. Therefore, ferrate has thedistinction of being an “environmentally safe” oxidant. Although theoxidation reactions with ferrate appear similar to those known for MnO₄⁻ and CrO₄ ²⁻, ferrate exhibits greater functional group selectivitywith higher rate of reactivity in its oxidations and generally reacts toproduce a cleaner reaction product.

One problem hindering ferrate implementation is difficulty in itspreparation. This difficulty may lead to increased production costs.Moreover, in addition to cost, the current methods known for producing acommercially useful and effective ferrate product, and the results ofthese methods, have been less than satisfactory. There exists a need fornew synthetic preparative procedures that are easier and less expensivein order to provide ferrate material at economically competitive prices.

Three approaches for ferrate synthesis are known: electrolysis,oxidation of Fe₂O₃ in an alkaline melt, or oxidation of Fe(III) in aconcentrated alkaline solution with a strong oxidant.

In the laboratory, by means of hypochlorite oxidation of iron (Fe(III))in strongly alkaline (NaOH) solution, the ferrate product has beenprecipitated by the addition of saturated KOH (G. Thompson, L. Ockerman,and J. Schreyer, J. Am. Chem. Soc., Vol. 73, pp. 1379-81 (1951)):

2Fe³⁺+3OCl⁻+10OH⁻→2FeO₄ ²⁻+3Cl⁻+5H₂O

The resulting purple solid is stable indefinitely when kept dry.

Commercial production of ferrate typically uses a synthetic schemesimilar to the laboratory preparation, also involving a hypochloritereaction. Most commonly, using alkaline oxidation of Fe(III), potassiumferrate (K₂FeO₄) is prepared via gaseous chlorine oxidation in causticsoda of ferric hydroxide, involving a hypochlorite intermediate. Anothermethod for ferrate production was described by Johnson in U.S. Pat. No.5,746,994.

A number of difficulties are associated with the production of ferrateusing the method described above. For example, several requirements forreagent purity must be ensured for maximized ferrate yield and purity.However, even with these requirements satisfied, the purity of thepotassium ferrate product still varies widely and depends upon manyfactors, such as reaction time, temperature, purity of reagents, andisolation process. Ferrate prepared this way generally containsimpurities, with the major contaminants being alkali metal hydroxidesand chlorides and ferric oxide. However, samples of this degree ofpurity are unstable and readily decompose completely into ferric oxides.

Other than the specific problems with product impurities andinstability, there also exist mechanical problems associated with theisolation of the solid ferrate product, such as filtering cold lyesolutions having a syrupy consistency.

Other processes for preparation of ferrates are known and used, many ofthem also involving the reactions with hypochlorite. For example, U.S.Pat. No. 5,202,108 to Deininger discloses a process for making stable,high-purity ferrate(VI) using beta-ferric oxide (beta-Fe₂O₃) andpreferably monohydrated beta-ferric oxide (beta-Fe₂O₃.H₂O ), where theunused product stream can be recycled to the ferrate reactor forproduction of additional ferrate.

U.S. Pat. Nos. 4,385,045 and 4,551,326 to Thompson disclose a method fordirect preparation of an alkali metal or alkaline earth metal ferratesfrom inexpensive, readily available starting materials, where the ironin the product has a valence of +4 or +6. The method involves reactingiron oxide with an alkali metal oxide or peroxide in an oxygen freeatmosphere or by reacting elemental iron with an alkali metal peroxidein an oxygen free atmosphere.

U.S. Pat. No. 4,405,573 to Deininger et al. discloses a process formaking potassium ferrate in large-scale quantities (designed to be acommercial process) by reacting potassium hydroxide, chlorine, and aferric salt in the presence of a ferrate stabilizing compound.

U.S. Pat. No. 4,500,499 to Kaczur et al. discloses a method forobtaining highly purified alkali metal or alkaline earth metal ferratesalts from a crude ferrate reaction mixture, using both batch andcontinuous modes of operation.

U.S. Pat. No. 4,304,760 to Mein et al. discloses a method forselectively removing potassium hydroxide from crystallized potassiumferrate by washing it with an aqueous solution of a potassium salt(preferably a phosphate salt to promote the stability of the ferrate inthe solid phase as well as in aqueous solution) and an inorganic acid atan alkaline pH.

U.S. Pat. No. 2,758,090 to Mills et al. discloses a method of makingferrate, involving a reaction with hypochlorite, as well as a method ofstabilizing the ferrate product so that it can be used as an oxidizingagent.

U.S. Pat. No. 2,835,553 to Harrison et al. discloses a method, using aheating step, where novel alkali metal ferrates with a valence of +4 areprepared by reacting the ferrate(III) of an alkali metal with the oxide(or peroxide) of the same, or a different, alkali metal to yield thecorresponding ferrate(IV).

U.S. Pat. No. 5,284,642 to Evrard et al. discloses the preparation ofalkali or alkaline earth metal ferrates that are stable and industriallyusable as oxidizers, and the use of these ferrates for water treatmentby oxidation. Sulfate stabilization is also disclosed.

The development of an economical source of ferrate is desired to derivethe benefits associated with ferrate application in a wide range ofprocesses. In view of the difficulties associated with the previouslyknown methods for preparing ferrates and the problems inherent in theferrate produced by these known methods, there is therefore an existingneed for a new preparative method for ferrate that is easy, convenient,safe and inexpensive, and that avoids both the chemical and mechanicalproblems. There also exists a need for a system which reduces orcounteracts the limited stability of ferrate, and systems which employferrate as an environmentally friendly oxidant and disinfectant.

SUMMARY OF THE INVENTION

A method of continuously synthesizing ferrate is disclosed, comprisingmixing a mixture comprising an iron salt and an oxidizing agent in amixing chamber; delivering at least a portion of the mixture to areaction chamber; continuously generating ferrate in the reactionchamber; delivering at least a portion of the ferrate to a site of usethat is proximal to the reaction chamber; and adding additional ironsalt and oxidizing agent to the mixing chamber.

Also disclosed is a method of treating, at a site of use, a mixturehaving at least one impurity, comprising continuously generating ferratein a reaction chamber located proximal to the site of use; contactingthe ferrate with the mixture at the site of use, whereby at least aportion of the impurity is oxidized.

Also disclosed is a device for continuously synthesizing ferrate,comprising a first holding chamber; a second holding chamber; a mixingchamber controllably connected to the first holding chamber and to thesecond holding chamber, into which a content of the first holdingchamber and a content of a second holding chamber are added to form amixture; a reaction chamber controllably connected to the mixingchamber, into which the mixture is kept for a period of time; and anoutput opening in the reaction chamber through which the mixture may betransported to a proximal site of use.

Also disclosed is a system for continuously synthesizing ferrate,comprising a first holding chamber containing an iron salt; a secondholding chamber containing an oxidizing agent; a mixing chambercontrollably connected to the first holding chamber and to the secondholding chamber, into which the iron salt and the oxidizing agent arecontrollably added to form a mixture; a reaction chamber controllablyconnected to the mixing chamber, into which the mixture is kept for aperiod of time, and in which ferrate is synthesized, and an outputopening in the reaction chamber through which the ferrate may betransported to a proximal site of use. The “period of time” during whichthe mixture is kept in the reaction chamber may range from seconds tohours to days, but may be any time longer than zero seconds.

Also disclosed is a method of continuously synthesizing ferrate,comprising providing a mixture of an iron salt and an oxidizing agent;continuously delivering at least a portion of the mixture to a heatingchamber; exposing the mixture to elevated temperatures in the heatingchamber, thereby generating ferrate; removing at least a portion of thegenerated ferrate from the heating chamber; adding additional mixture tothe heating chamber.

Also disclosed is a device for continuously synthesizing ferrate,comprising a holding chamber; a mover controllably connected to theholding chamber such that at least a portion of a content of the holdingchamber is transferred to the mover; a heating chamber, through which atleast a portion of the mover moves; an output opening in the heatingchamber through which the content on the mover may be transported to aproximal site of use.

Also disclosed is a device for continuously synthesizing ferrate,comprising a mixing chamber comprising two electrodes, where theelectrodes provide sufficient electric current to convert a solution ofan iron salt to a solution of ferrate; a reaction chamber controllablyconnected to the mixing chamber, into which the mixture is kept for aperiod of time; and an output opening in the reaction chamber throughwhich the mixture may be transported to a proximal site of use. Themixture is kept in the reaction chamber for a period of time longer thanzero seconds.

Also disclosed is a method of continuously synthesizing ferrate,comprising continuously providing an aqueous solution comprising an ironsalt in a mixing chamber, where the mixing chamber comprises at leasttwo electrodes; providing sufficient electric current to the at leasttwo electrodes to convert at least a portion of the iron salt toferrate; delivering at least a portion of the ferrate to a site of usethat is proximal to the reaction chamber; and adding additional aqueoussolution to the mixing chamber.

Also disclosed is a method of synthesizing ferrate, comprising mixing amixture comprising an iron salt and an oxidizing agent in a mixingchamber; delivering at least a portion of the ferrate to a site of usethat is proximal to the mixing chamber.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts an embodiment of the device for solution phase synthesisof ferrate ion.

FIG. 2 depicts an embodiment of the device for solid phase synthesis offerrate ion.

FIG. 3 depicts an embodiment of the device for electrochemical synthesisof ferrate ion.

FIG. 4 is a flow chart depicting some embodiments of the process ofgenerating and purifying ferrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is an object of the invention to provide a new, convenient,inexpensive, and safe method for producing a salt of ferrate. Such amethod may produce the sodium salt, but may be used to prepare othersalts of Group I or Group II cations, or other cations, whether metallicor not.

It is an object of the invention to provide an environmentally friendlyoxidant for application in a variety of wastewater contaminants andwater treatment problems. Such an oxidant produces a cleaner reactionproduct(s) and thereby may be used to replace existing environmental,laboratory, and industrial oxidants which may have deleterious sideeffects or costs.

It is an object of the invention to provide a new, safe, and inexpensiveindustrial and environmental remediation chemical oxidant that overcomesthe problems associated with known oxidants for water treatment (forexample, chlorine, hypochlorite, chlorine dioxide, permanganate, andozone) and the by-products of these oxidants.

It is an object of this invention to provide a new ferrate product to beused in the control of sulfides, including hydrogen sulfide gas, insewer systems, ground water, treatment plants, and waste treatmentfacilities.

It is an object of the invention to provide an improved ferrate productfor remediation of uranium, transuranics, rocket fuel propellantcontaminants (hydrazine and monomethylhydrazines) and mustard gas.

It is a further object of the invention to provide an innovative productto be used as coagulant and disinfectant.

It is an object of the present invention to provide an oxidant to beused in drinking water disinfection and coagulation, biofouling control,ground water decontamination, solid surface washing, and hazardous wastetreatment.

It is an object of the present invention to provide an oxidant to beused in synthetic chemistry.

It is an object of the present invention to provide an oxidant to beused in surface preparation, including polymer surface and metallicsurface preparation.

To achieve at least one of the above-stated objectives, the followingmethods, manufactures, compositions of matter, and uses thereof areprovided.

I. On-Site Generation

The inventors have discovered that many of the presently unaddressedproblems associated with ferrate use relate to the purification andstorage of ferrate. Therefore, in some embodiments of the invention, asystem of producing ferrate and using it without substantially furtherpurification, packaging, or preparation is provided. Because ferrate, inits unpurified form decomposes rather rapidly, the ferrate produced bythe provided methods need not be stored. Ferrate may, and preferably is,used immediately, or substantially soon after its generation. Therefore,certain embodiments of the present invention provide a device that isdesigned to be located in close proximity to the site of use, such thatwhen ferrate is produced, it may be rapidly and efficiently delivered tothe site of use, without substantial further purification, packaging,shipping, transfer, or preparation.

As used herein, the terms “site of generation” or “generation site”refer to the site where the device for the generation of ferrate islocated. In one embodiment exemplified herein, the generation siteincludes a reaction chamber for generation of ferrate. The terms “siteof use,” “use site,” or “treatment site” refer to the site where theferrate is contacted with the object it is to oxidize, synthesize,disinfect, clean, plate, encapsulate, or coagulate.

The terms “close proximity” and “proximal” are used interchangeablyherein. These terms are used to refer to the relative locations of thegeneration site and the use site when the two sites are within adistance that allows for the ferrate to travel the distance within ahalf-life of its decomposition. “Half-life” of a decomposition isunderstood to be the amount of time it takes for one half of thematerial present to undergo decomposition. The half-life for any givenferrate composition will depend on the conditions under which theferrate is generated and/or stored. Thus, for example, the temperature,concentration of base, concentration of oxidizing agent and presence ofimpurities will all tend to affect the half-life of the ferratecomposition. However, the half-life can be readily measured by thosehaving ordinary skill in the art using conventional techniques.Therefore, a generation site is “proximal” to a use site when theconcentration of ferrate at the use site at the time of delivery isequal to or greater than one-half of the concentration of ferrate at thegeneration site. The distance between the generation site and the usesite is defined in terms of the half-life and a length of time requiredfor delivery, rather than simply in terms of physical displacement.Thus, the physical displacement between a generation site and use sitethat are in close proximity may vary depending on the half-life of theferrate composition being delivered between the two sites and the rateat which the composition is delivered. Accordingly factors affectingboth the rate of ferrate transfer and factors affecting the half-lifewill all affect the maximum physical displacement permissible for thetwo sites to remain in close proximity. Factors affecting the rate offerrate transfer include, but are not limited to, the pressure generatedby a pump used in the transfer and the size of the plumbing used in thetransfer.

The on-site generation methods provide a number of advantages over knownprocesses. Initially, because the produced ferrate can be used withoutfurther substantial purification or stabilization, there is no need forstorage or shipping. In addition, eliminating the need for a highlypurified ferrate ultimately saves costs by increasing the yield of thereaction because less starting materials are needed to afford the sameamount of usable ferrate.

The current practice for making and purifying ferrate involves theproduction of sodium ferrate using sodium hydroxide, followed by theprecipitation of potassium ferrate using potassium hydroxide. Thus, thecurrent methods use base in two distinct steps. The methods of some ofthe embodiments of the present invention require substantially less baseto produce usable ferrate since the methods do not require the additionof potassium hydroxide to sodium ferrate.

Thus, the ferrate produced by some of the methods of the presentinvention can be used or purified in a solution-to-solution phasemanner, i.e., ferrate is generated in the solution phase and is used inthe solution phase, without the intervening crystallization, orconversion to the solid phase (i.e., solution-to-solid phase). Ifpartial purification or separation is required, then such purificationor separation can be achieved in the solution phase as well. In certainembodiments of the present invention, the produced ferrate is notconverted to any phase other than the solution phase.

The solution-to-solution phase concept discussed above providesadvantages over the solution-to-solid phase method. For example, asdiscussed above, conversion to solid or crystallization is limited bythe nature of the counter-ion. Crystallization of potassium ferrate isless difficult than crystallization of sodium ferrate. Ferrate withcertain counter-ions can never be crystallized or can be crystallizedunder very difficult conditions. Using the solution-to-solution phaseconcept, virtually any counter-ion can be used. In addition, onceferrate is crystallized, it would have to be re-dissolved in aqueousmedia for use. The re-dissolution of ferrate adds both cost (loss offerrate, addition of water, and dissolution tanks, to name a few) andtime (dissolution time) to the process. In the solution-to-solutionphase method, ferrate is already in aqueous solution and can be used assuch. Furthermore, if pH is to be adjusted, it is more efficient toadjust the pH of the ferrate stream once it is produced than to adjustthe pH of a ferrate solution prepared from adding solid ferrate towater. Yet another advantage of the solution-to-solution phase conceptis the ease of production of custom blends.

The above advantages result in the entire process being cheaper and moreeconomical than the available processes. The relatively low cost ofproduction allows the ferrate to be used in a large variety of settings,which heretofore have been substantially unavailable for the oxidizingbenefits of the compound due to its cost. Most importantly, ferrate maynow be made available to municipal water and wastewater treatmentfacilities, which are cost conscious.

Furthermore, on-site generation of ferrate allows the end user tocontrol the amount of ferrate to be produced. This may alleviate orreduce the need for inventory control of ferrate, in addition toalleviating or reducing the need to store ferrate.

II. Process for Preparing Ferrate

A. Solution Phase Production

In one aspect, the invention relates to a method of continuouslysynthesizing ferrate, comprising mixing an iron salt and an oxidizingagent in a mixing chamber to form a mixture; delivering at least aportion of the mixture to a reaction chamber; continuously generatingferrate in the reaction chamber; delivering at least a portion of theferrate to a site of use that is proximal to the reaction chamber; andadding additional iron salt and oxidizing agent to the mixing chamber.

In certain embodiments, the above method further comprises the additionof a solvent during the mixing step. In some embodiments, the solvent iswater and the mixture is, therefore, an aqueous solution. In otherembodiments, the mixture is a non-aqueous solution. In certain otherembodiments, the oxidizing agent may be a neat liquid, in which case itwould act as a solvent for dissolving the iron salt as well. In stillother embodiments, the iron salt and the oxidizing agent are added assolids, and the reaction takes place in solid form.

Thus, one embodiment of the invention relates to a method ofcontinuously synthesizing ferrate, comprising mixing an aqueous solutioncomprising an iron salt and an oxidizing agent in a mixing chamber;delivering at least a portion of the aqueous solution to a reactionchamber; continuously generating ferrate in the reaction chamber;delivering at least a portion of the ferrate to a site of use that isproximal to the reaction chamber; and adding additional aqueous solutionto the mixing chamber.

It is known to those of skill in the art that iron can accommodate anoxidation state in the range of 0 to +8, including the +1, +2, +3, +4,+5, +6, and +7 oxidation states. Iron in the 0 oxidation state iselemental iron. Most compounds and salts of iron found in nature have anoxidation state of either +2 (Fe(II)) or +3 (Fe(III)). In the context ofthe present invention, “ferrate” refers to an ion comprising iron in its+4, +5, +6, +7, or +8 oxidation states, i.e., comprising Fe(IV), Fe(V),Fe(VI), Fe(VII), or Fe(VIII). The ferrate ion also contains oxygenatoms. It may or may not comprise atoms of other elements. Furthermore,“ferrate” may also refer to a mixture of ions comprising iron in variousoxidation states, as long as at least a portion of the ions compriseiron exhibiting an oxidation state of +4 or higher. Thus, for example,ferrate refers to a FeO₄ ²⁻, where the iron is Fe(VI) and the otheratoms in the ion are oxygen atoms. A solution comprising FeO₄ ²⁻ ionsmay also contain ions exhibiting iron in its +5 oxidation state, or anyother oxidation state, including the elemental form of iron, and itwould still be called ferrate. Similarly, a ferrate solution may containno Fe(VI) containing ions. A ferrate solution may also comprise Fe(V) orFe(IV) containing ions. Therefore, any ion comprising Fe(IV), or higheroxidation state iron atoms, and at least one oxygen atom is consideredto be “ferrate.” Ferrate ions may be either cations or anions.

It is understood by those skilled in the art that any ion requires acounterion of equal, though opposite, charge. This is also true for theferrate ions of the present invention. The counterion may be any ionthat renders neutral the overall charge of the mixture comprising theferrate ion. When ferrate is an anion, the counterion may be any cation.The most common form of ferrate to-date is K₂FeO₄, where the iron is inits +6 oxidation state, the ferrate is an anion and the counterion ispotassium. Any other counter-cation, such as, and without limitation,sodium, calcium, magnesium, silver, etc., may also be present.

By “continuously generating” or “continuously synthesizing” it is meantthat once ferrate begins to be delivered to the reaction chamber, therecontinues to be an amount of ferrate in the reaction chamber for theduration of time that the method is being practiced. Thus, as describedhereinbelow in greater detail, in one embodiment of a continuousgeneration process in accordance with the present invention, there is aconstant flow of material from the mixing chamber to the reactionchamber. In other embodiments, as also described hereinbelow, materialis intermittantly transferred from the mixing chamber to the reactionchamber while maintaining at least some ferrate in the reaction chamber.

In certain embodiments, the additional mixture of iron salt andoxidizing agent of the above method is added in an amount tosubstantially replace the portion of the mixture delivered to thereaction chamber. In the context of the present invention, for a secondamount to substantially replace a first amount, the second amount may beless than, equal to, or greater than the first amount.

In certain embodiments, the method of producing ferrate furthercomprises adding a base to the mixture. The base may comprise a nitrogenbase or an ion selected from the group consisting of hydroxide, oxide,sulfonate, sulfate, sulfite, hydrosulfide, phosphate, acetate,bicarbonate, and carbonate, or a combination thereof. “Nitrogen bases”are selected from acyclic and cyclic amines. Examples of nitrogen basesinclude, but are not limited to, ammonia, amide, methylamine,methylamide, trimethylamine, trimethylamide, triethylamine,triethylamide, aniline, pyrrolidine, piperidine, and pyridine, or saltsthereof.

To produce ferrate by the methods of the present invention, an iron saltmust be provided. “Iron salt” or “salt of iron” refers to a compoundthat comprises an iron atom in an oxidation state other than zero. Theiron salt used by the methods of the present invention may be producedin situ, i.e., by oxidizing elemental iron either chemically orelectrochemically prior to its introduction into the mixing chamber orby performing the oxidation inside the mixing chamber. The iron atom inthe iron salt will have an oxidation state greater than zero, preferably+2 or +3, though this oxidation state may be reached transiently as theiron atom is converted from its starting oxidation state to the finaloxidation state of +4 or above.

In certain embodiments, the iron salt may be selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxides, ferrous oxides, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof. All different forms of ferric and ferrous oxideare contemplated to be used with the methods of the present invention.

In some embodiments of the present invention, ferrate is produced bychemical oxidation of the iron salt. The chemical oxidation is performedby mixing an oxidizing agent, or a solution containing the oxidizingagent, with the iron salt, or with the solution containing the ironsalt. In some embodiments, the oxidizing agent, or a solution containingthe oxidizing agent, is added to the iron salt, or to the solutioncontaining the iron salt, whereas in other embodiments, the iron salt,or the solution containing the iron salt, is added to the oxidizingagent, or to a solution containing the oxidizing agent. An “oxidizingagent” is a chemical compound that oxidizes another compound, and itselfis reduced. In certain embodiments, the oxidizing agent comprises atleast one of the following: a hypohalite ion, a halite ion, a halateion, a perhalate ion, ozone, OXONE®, halogen, a peroxide, a superoxide,a peracid, a salt of a peracid, and Caro's acid, or a combinationthereof.

Embodiments of the invention include those in which the oxidizing agentcomprises a hypohalite ion selected from the group consisting of thehypochlorite ion, the hypobromite ion, and the hypoiodite ion. In otherembodiments of the invention, the oxidizing agent comprises a halite ionselected from the group consisting of the chlorite ion, the bromite ion,and the iodite ion. In yet other embodiments of the invention, theoxidizing agent comprises a halate ion selected from the groupconsisting of the chlorate ion, the bromate ion, and the iodate ion.Certain other embodiments of the invention include those in which theoxidizing agent comprises a perhalate ion selected from the groupconsisting of the perchlorate ion, the perbromate ion, and the periodateion.

Thus, in an embodiment of the present invention, an aqueous solution ofan iron salt and an oxidizing agent is mixed in a mixing chamber. Abase, or a combination of bases, may also be added to the mixing chamberat this time. The solution is mixed in the mixing chamber for a certainperiod of time, which may range from seconds to hours depending on theconditions of the mixing, e.g., the temperature or the concentration ofthe ingredients. Those skilled in the art recognize that at this stageferrate production begins.

As the mixing is taking place, at least a portion of the mixture isdelivered to a reaction chamber. The mixture is held in the reactionchamber for a certain period of time until the amount of ferrate in themixture, e.g., the concentration of ferrate in an aqueous solution,reaches a pre-determined level. The concentration of ferrate for use isdetermined based on the need for the ferrate and the conditions for thesynthesis or use. Certain applications may require higher yields offerrate than others. Therefore, the time that mixture remains in thereaction chamber may range from seconds to hours. The reaction chambermay also be used as a “holding tank,” i.e., a place to keep thegenerated ferrate, at a certain temperature, to be used at a later time.The holding tank may be at room temperature, or at a temperature that iseither higher or lower than room temperature. The mixture containing theferrate is then removed from the reaction chamber and is delivered tothe site of use. The site of use is “proximal” to the reaction chamber.

In certain embodiments, as the mixture is removed from the mixingchamber to the reaction chamber, additional iron salt and oxidizingagent is added to the mixing chamber. In other embodiments, additionaliron salt and oxidizing agent is added to the mixing chamber after allof the mixture within the mixing chamber has been transferred to thereaction chamber. It is contemplated in some of the embodiments of thepresent invention that the flow of the mixture from the mixing chamberto the reaction chamber is continuous. Therefore, while ferrate isneeded, new batches of the mixture are to be added to the mixingchamber.

In some of the embodiments of the present invention, in addition to theiron salt, a metal oxide is added to the mixture. The metal oxide may beadded at any point during the production of ferrate, either as anoriginal ingredient, or in the mixing chamber, or in the reactionchamber, or anywhere along the path. The metal oxide may also be addedto a mixture comprising ferrate subsequent to the production of ferrate,when ferrate is being contacted, or after ferrate has been contacted,with the object to be synthesized, cleaned, disinfected, oxidized, orcoagulated. The metal atom of the metal oxide may be a main group metal,a transition metal, or an f-block metal. A “transition metal” is a metalwithin columns 3-12 of the periodic table, i.e., metals in the scandium,titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper,and zinc triads. An “f-block metal” is a metal in the lanthanide oractinide series, i.e., metals with atomic numbers 57-71 and 89-103.Thus, lanthanum and actinium are both transition metals and f-blockmetals. The metal oxide may be scandium oxide, titanium oxide, vanadiumoxide, manganese oxide, cobalt oxide, nickel oxide, copper oxide, zincoxide, gallium oxide, yttrium oxide, zirconium oxide, niobium oxide,molybdenum oxide, ruthenium oxide, rhodium oxide, palladium oxide,silver oxide, cadmium oxide, indium oxide, tin oxide, hafnium oxide,tantalum oxide, tungsten oxide, rhenium oxide, osmium oxide, iridiumoxide, platinum oxide, or any salt containing the oxides of thesemetals.

In certain embodiments, the solution comprising ferrate is irradiatedwith light before or during use. In other embodiments, the solutioncomprising ferrate is kept in the dark before use. When the solution isirradiated with light, the light may be a light of any frequency withinthe electromagnetic spectrum, i.e., anywhere between radio waves andx-rays and gamma radiation, including ultraviolet light, visible light,or infrared light.

Certain other embodiments of the present invention are directed to a“batch process,” during which ferrate is generated once. Thus, theseembodiments of the present invention are directed to a method ofsynthesizing ferrate, comprising adding an aqueous solution comprisingan iron salt and an oxidizing agent in a mixing chamber; mixing theaqueous solution; delivering at least a portion of the aqueous solutionto a reaction chamber; and delivering at least a portion of the ferrateto a site of use that is proximal to the reaction chamber.

In certain embodiments, the ferrate generated by the above method in themixing chamber is delivered to the site of use without being deliveredto a separate reaction chamber. In these embodiments, therefore, themixing chamber and the reaction chamber are one and the same. In certainother embodiments, after the mixing in the mixing chamber, the ferratesolution is delivered to a holding tank where it is kept until its useis needed. In any event, the ferrate solution is held for a period oftime that is less than or equal to the half-life of the ferrate in thesolution under the conditions (i.e., temperature, concentration, pH,etc.) it is held.

B. Solid State Production

In another aspect, the invention relates to a method of continuouslysynthesizing ferrate, comprising providing a mixture of an iron salt andan oxidizing agent; continuously delivering at least a portion of themixture to a heating chamber; exposing the mixture to elevatedtemperatures in the heating chamber, thereby generating ferrate;removing at least a portion of the generated ferrate from the heatingchamber; adding additional mixture to the heating chamber.

In certain embodiments, the exposure of the mixture to elevatedtemperatures and the removal of ferrate from the exposure is continuous.

In some embodiments, the additional mixture added to the heating chamberis in an amount to substantially replace the portion of the ferrateremoved from the heating chamber.

By “continuously delivering” it is meant that once the mixture of ironsalt and oxidizing agent begins to be delivered to the heating chamber,it continues to be delivered to the heating chamber for the duration oftime that the method is being practiced.

In certain embodiments of the invention, a base, as described herein, isalso added to the mixture.

In some of the embodiments of the present invention, the mixture of theiron salt and the oxidizing agent is carried through the heating chamberon a belt. The belt is made of materials that can withstand temperatureshigher than room temperature. These materials may include, but not belimited to, rubber, steel, aluminum, glass, porcelain, etc.

In certain embodiments of the invention the mixture is poured directlyonto the belt, whereas in other embodiments, the mixture is poured intocontainers and the containers are placed on the belt. In any of theseembodiments, the surface that comes to contact with the mixture is notreactive towards ferrate or other oxidants.

The heating chamber is heated to temperatures higher than roomtemperature. “Room temperature” is about 20° C. In some embodiments theheating chamber is heated to a temperature of between about 20° C. andabout 1000° C., or between about 50° C. to about 500° C., or betweenabout 100° C. to about 400° C. By “about” a certain temperature it ismeant that the temperature range is within 40° C. of the listedtemperature, or within 30° C. of the listed temperature, or within 20°C. of the listed temperature, or within 10° C. of the listedtemperature, or within 5° C. of the listed temperature, or within 2° C.of the listed temperature. Therefore, by way of example only, by “about400° C.” it is meant that the temperature range is 400±40° C. in someembodiments, 400±30° C. in some embodiments, 400±20° C. in someembodiments, 400±10° C. in some embodiments, or 400±5° C. in otherembodiments, or 400±2° C. in still other embodiments. In someembodiments the temperature remains relatively constant throughout theprocess whereas in other embodiments the temperature varies during theprocess. In the embodiments where the temperature varies, thetemperature may be ramped up, i.e., the final temperature is higher thanthe initial temperature, or ramped down, i.e., the final temperature islower than the initial temperature.

Thus, in some embodiments of the present invention, a mixture of an ironsalt and an oxidizing agent is put on a belt. The iron salt and theoxidizing agent may be pre-mixed prior to addition to the belt, or theymay be mixed subsequent to addition to the belt. The mixture may beadded directly onto the belt or may be added to containers that areplaced on the belt. The mixture may be added to the containers beforethe containers are put on the belt or the mixture may be added to thecontainers while the containers are on the belt. In certain embodiments,base is also added to the mixture at some point.

The belt then moves through a heating chamber, thereby heating themixture. The heat must be sufficient to produce ferrate in the mixture.The speed of the belt through the heating chamber, the length of timethe mixture is heated, and the temperature to which the mixture isheated are all adjustable. Thus, the mixture may be heated for secondsor for hours.

Subsequent to the heating event, the heated mixture, now comprisingferrate, is removed from the belt. The belt then returns to the originallocation for the addition of more of the mixture. It is contemplatedthat the movement of the belt through the heating chamber is continuous.

In some embodiments, the mixture exposed to elevated temperature in theabove method is a solid.

C. Electrochemical Production

In another aspect, the invention relates to a method of continuouslysynthesizing ferrate, comprising providing an aqueous solutioncomprising an iron salt in a reaction chamber, where the reactionchamber comprises at least two electrodes; providing sufficient electriccurrent to the at least two electrodes to convert at least a portion ofthe iron salt to ferrate; continuously delivering at least a portion ofthe ferrate to a site of use that is proximal to the reaction chamber;and adding additional aqueous solution to the reaction chamber tosubstantially replace the portion of the aqueous solution delivered tothe holding chamber.

By “continuously delivering” it is meant that once ferrate begins to bedelivered to the site of use, it continues to be delivered to the siteof use for the duration of time that the method is being practiced.

In certain embodiments of the invention, base is added to the aqueoussolution, while in other embodiments, acid is added.

The reaction chamber comprises two electrodes. The electrodes aredesigned to conduct electricity through the aqueous solution, therebyconverting the iron of the iron salt to ferrate in an electrochemicalreaction. The iron of the iron salt may have been added to the solutionas an iron salt, or may be the dissolved iron electrode, which becamedissolved upon the introduction of electricity. It is contemplated thatas solution containing ferrate is removed from the reaction chamber,additional aqueous solution is added to the mixing chamber foradditional reactions. In certain embodiments, the flow of materials fromthe reaction chamber to the holding chamber is continuous.

D. Other Examples of Methods of Ferrate Production

In one embodiment, ferric sulfate particles may be added to a staticmixer and mixed in an aqueous medium. The static mixer includes a mixingmechanism that is capable of microparticulating particles. Static mixersmay be continuous radial mixing devices, characterized by plug flow orany other conventional mixer. Static mixers are preferred in that theyhave short residence times and little back mixing. Thus, proper dosingof feed components with no fluctuation in time is a prerequisite forgood performance.

Another desirable feature of static mixers is that they have no movingparts for mixing. The absence of moving parts and reliance on surfacearea and conformation for reactant/product movement reduces the need forcoolant to cool the reaction. Thus, static mixers are comparatively lowmaintenance pieces of equipment. The static mixers used in the processesof the present invention may be incorporated into pump-around loopreactors or in cascade type reactors, such as those manufactured byKoch, i.e., The Koch-SMVP packing /Rog 92/. Other static mixers includeKoch type SMF, SMXL-R, SMXL, SMX and SMV type.

For other embodiments, a micro reactor is used for mixing reactants.Micro-reactors and static mixers are usable to make ferrate in acontinuous process or a semi-continuous process.

The mixing mechanism may be a tortuous path, a mixing device or anaspirator. OXONE® or Caro's Acid or other strong oxidant in container isadded to the static mixer. The term “OXONE” as used herein refers topotassium peroxymonopersulfate or potassium monopersulfate. Reactionbegins instantaneously and generates heat. The temperature of thereaction is adjusted through the use of a cooling coil or cooling jacketto a temperature of about −10° C. Temperature is controlled through afeed forward feed back control mechanism. Water is employed as atransport medium for transporting the ferric sulfate, oxidant andreaction products. The volume of the water is minimized to a volume thatmaximizes ferrate production yield.

An amount of dry KOH may be added that is effective to maximize ferrateproduction. The KOH is added to another micro mixer or static mixer KOHis added to a main reactor. The KOH is cooled to about −10° C. prior tointroduction to the main reactor. The main reactor is also a staticmixer.

An excess of KOH prevents conversion of Fe(III) to ferrate. The use ofstatic mixers maximize surface area available for reaction for all ofthe reactants. It is believed that the use of a static mixer or micromixer speeds up the reaction process.

A use of Caro's acid is preferred in that it aids in stabilizing ferratebecause sulfate from the Caro's acid “buffers” the ferrate. It isunderstood, however, that if the static mixer is positioned proximal towater or wastewater to be treated, sulfate stabilization is optional andFe(0) oxidation can occur with another oxidant, such as chlorine orperoxide.

The temperature in the reactor is preferably maintained at about 40° C.,but may be as low as 20° C. or as high as 60° C. As products are removedfrom the reactor, the temperature in the product stream is graduallydecreased to room temperature.

A use of a static mixer permits a method of water treatment thatincludes shocking an iron moiety with an oxidant, quenching the reactionwith KOH and injecting the ferrate into a water or wastewater or sludgestream. The use of a static mixer renders a complex chemical reactionperformable by operators of water and waster treatment plants. Becauseof the microparticulation of iron species and very rapid mixing,conventional concerns about temperature control are substantiallyeliminated.

In one other embodiment ferrate is produced in a continuous process byhypochlorite oxidation of iron (III) in a strongly alkaline solution andis precipitated by the addition of saturated KOH. Hypochlorite used inferrate synthesis is formed by disproportionation of chlorine in a coldcaustic soda solution:

Cl₂+OH⁻→Cl⁻+OCl⁻+H⁺.

Ferrate ion may be produced by adding a material such as ferric nitrateto the hypochlorite solution described:

10OH⁻+3OCl⁻+2Fe³⁺→2FeO₄ ²⁻+3Cl⁻+5H₂O

Synthesis of ferrate begins by addition of KOH solutions to a cold-waterjacketed reactor set between 20° C. and 40° C. Gaseous or liquidchlorine is bubbled through the liquid reaction mixture, and the solidiron salt or oxide is added. Atmospheric pressure is maintained in thereactor. The ranges of mole ratios of reactants, Cl₂, KOH, Fe(III), are1.5-30:10-60:1. The smaller ratios decrease product yields, while thelarger ratios require larger recycle streams back to the reactor, leaveKOH unused, or accelerate ferrate decomposition.

The average residence time of the ferrate in the reactor is 180 minutes.Residence times greater than 30 minutes lead to significant ferratedecomposition. The product mixture leaving the reactor is typically 2-6%potassium ferrate by weight.

The reaction mixture includes solid K₂FeO₄, KCl, and Fe(OH)₃ and aqueousKOH, KOCl, KCl, and a small amount of K₂FeO₄. The KOH concentration inthis mixture is increased to 35-45% by weight to further precipitate theferrate from solution. The temperature is lowered during this process to5-20° C. to maximize the yield of solid potassium ferrate. The crudesolid product is separated by centrifugation within 5 minutes offinishing the KOH addition and the liquids are recycled back to thereactor.

The crude product is contaminated with KCl and Fe(OH)₃. Selectivelydissolving the potassium ferrate into 10-20% KOH (aq), by weight, at20-50° C., purifies the product. The KCl and Fe(OH)₃ are insoluble inthis media and are removed by centrifugation. The solids may beseparated and reprocessed for use as starting materials in ferrateproduction.

The ferrate ion may be reprecipitated by addition of concentration KOHsolutions, 40-55% by weight, or solid KOH. When the resulting mixture is30%, crystals of K₂FeO₄ precipitate when the solution is cooled tobetween −20 and 0° C. As in the earlier separation steps, the solid iscollected by centrifugation. The separated KOH solutions may be recycledto the ferrate reactor.

The potassium ferrate produced may be washed in a tank with anhydrousDMSO to remove any entrapped KOH or water. The DMSO is recovered byflash evaporation. Next, the solid is transferred to a methanol washtank for further purification. The solid is finally collected bycentrifugation. The methanol is recovered by distillation.

In another embodiment reactants described above are added to a reactorcooled to a temperature of 20° C. After about 180 minutes, reactionproducts are treated with KOH, to solubilize any precipitated ferrateand the entire mixture is transferred to water or wastewater or sludgefor treatment. For one embodiment, effluent from the reactor includesunreacted ferric sulfate, unreacted OXONE®, potassium sulfate, KOH andabout 20% dissolved ferrate. The presence of KOH and ferric ions retardthe decomposition rate with water as the product stream is being mixedwith untreated water.

The mixture containing the ferrate may be polished, if required.

In another embodiment hypochlorite is substituted for chlorine gas. Byintroducing NaCl to the reaction mixture, Na₂FeO₄ is precipitatedwithout any need for a KOH leaching step or extra equipment.

In another embodiment ferrate is generated as a solid in a fluidized bedreaction. The fluidized bed comprises one or more of FeCl₂, FeSO₄,Fe₂(SO₄)₃, Fe(NO₃)₃ and beta-ferric oxide monohydrate, oxygen gas andchlorine gas. The reaction occurs at a reduced temperature, such as 20°C. Crystals of ferrate are produced.

In one other embodiment ferrate is produced as a result of a directreaction of alkali peroxides, such as sodium peroxide or potassiumperoxide or potassium superoxide with hematite to produce potassium orsodium ferrate. The reaction is believed to proceed by these chemicalreactions:

Mole ratio Fe₂O₃ + 6 KO₂ → 2 K₂FeO₄ + K₂O + 3 O₂(g) 1 Fe₂O₃:6 K₂OFe₂O₃ + 3 K₂FeO₄ + K₂O 1 Fe₂O₃:3 K₂O₂ 1 Fe:3 K, for both

The temperature of reaction for this synthetic approach is about 400 to600° C. for a time of about 12 hours. It is believed that chemicalreaction occurs though a solid-solid contact, a liquid-solid contact ora vapor/solid contact. The liquid is a molten salt. The vapor is amaterial such as K₂O₂ vapor.

Reactants should be dry, of fine particle size and well mixed. Mixingshould avoid contact with air, as moisture and CO₂ will react withperoxide. Reactants should be held at 120 to 150° C. in a TGA in drynitrogen to thoroughly remove any adsorbed water prior to heating to theTGA reaction temperature.

When dissolved peroxide/superoxide reacts with hematite, it producesferrate, dissolved in a salt solution. Upon cooling, the dissolvedferrate ions precipitate from the salt as crystals of K₂FeO₄. A hightemperature route produces K₂FeO₄, but with modest yields and with arequirement of a subsequent processing step to separate the K₂FeO₄ fromthe salt mixture. In one embodiment, the salt mixture is not separatedand the entire mixture is used for water or wastewater treatment. Oneadvantage is that a simple process involving a single high temperaturereactor translates into a lower cost of production.

One other option is a two-step process. An inexpensive source ofperoxide/superoxide is processed in a first reactor to produce a gasstream containing peroxide/super oxide species. The gas stream is ductedinto a second reactor containing hematite, where a direct reaction iscarried out to produce ferrate. The temperatures of reactors A and B areseparately set to optimize respective processes. With this process, thefirst reactor temperature is about 1000° C. and the second reactortemperature is 400-500° C. The peroxide reaction may be performed in astatic mixer as described for a reaction of iron and Caro's acid.

While oxidants of OXONE®, Caro's acid, peroxide/superoxide, chlorine andhypochlorite are described herein, it is understood that other oxidantsmay be suitable for use. Some of these oxidants are described in anarticle on ferrate oxidants in Grazzino Italiano by Losanna. It isbelieved that enzymes may also be usable in ferrate process embodimentsof the present invention to reduce reaction temperature.

III. Device for On-Site Generation of Ferrate

A. Solution Phase Production Device

In another aspect, the invention relates to a device for continuouslysynthesizing ferrate for delivery to a site of use, comprising a firstholding chamber; a second holding chamber; a mixing chamber controllablyconnected to the first holding chamber and to the second holdingchamber, into which a content of the first holding chamber and a contentof a second holding chamber are added to form a first mixture; areaction chamber controllably connected to the mixing chamber, thereaction chamber adapted to receive the first mixture and maintain thefirst mixture for a period of time; a ferrate mixture in the reactionchamber; and an output opening in the reaction chamber through which theferrate mixture is adapted to be transported to the site of use, wherethe site of use is proximal to the reaction chamber.

In some embodiments the mixing chamber further comprises a mechanicalagitator.

In other embodiments, the mixing chamber comprises a tube configured tomix the mixture as it passes through the tube.

Certain embodiments of the invention relate to a device in which themixing chamber further comprises a temperature control device. Thetemperature control device may include a jacket around the mixingchamber whereby a cooled or heated fluid is passed through the jacket inorder to maintain the temperature of the intraluminal space at a certainpredetermined level.

Other embodiments of the invention further comprise a pump downstreamfrom the first and the second holding chambers and upstream from themixing chamber. The pump controls the flow of materials into the mixingchamber.

Some other embodiments of the invention further comprise a pumpdownstream from the mixing chamber and upstream from the reactionchamber. This pump controls the flow of material out of the mixingchamber and into the reaction chamber.

In some of the embodiments of the invention the reaction chambercomprises a tube located between the mixing chamber and the outputopening.

In another aspect the invention relates to a system for continuouslysynthesizing ferrate, comprising a first holding chamber containing aniron salt; a second holding chamber containing an oxidizing agent; amixing chamber controllably connected to the first holding chamber andto the second holding chamber, into which the iron salt and theoxidizing agent are controllably added to form a mixture; a reactionchamber controllably connected to the mixing chamber, into which themixture is kept for a period of time, and in which ferrate issynthesized, and an output opening in the reaction chamber through whichthe ferrate may be transported to a proximal site of use.

In some embodiments a base, as described herein, is added to themixture. The iron salt, the oxidizing agent, the mixing chamber, and thereaction chamber are as described herein.

In certain embodiments, the device of the invention further comprises apump downstream from the first and the second holding chambers andupstream from the mixing chamber. In other embodiments, the devicefurther comprises a pump downstream from the mixing chamber and upstreamfrom the reaction chamber.

FIG. 1 shows an embodiment of the solution state production device. Thefigure depicts two holding chambers 101. Other embodiments of theinvention may exhibit additional holding chambers, depending on thenumber of ingredients added initially. Some embodiments of the inventionmay exhibit only one holding chamber 101. The holding chambers areconnected to the mixing chamber 103. In some embodiments, the flow ofmaterial between the holding chambers 101 and the mixing chamber 103 maybe controlled. The flow is controlled either by the presence of a pumpor a valve (107) after each holding chamber 101, or by the presence of apump or a valve (109) before the mixing chamber 103, or by a combinationthereof. In certain embodiments, no pump or valve exists between theholding chamber 101 and the mixing chamber 103.

The mixing chamber 103 is connected to the reaction chamber 105. In someembodiments, the flow of material between the mixing chamber 103 and thereaction chamber 105 may be controlled. The flow may be controlled bythe presence of a pump or a valve (111) after the mixing chamber 103. Incertain embodiments, no pump or valve exists between the mixing chamber103 and the reaction chamber 105.

The reaction chamber 105 is connected with an output opening 115,through which the product of the reaction is transferred to the site ofuse. The flow from the reaction chamber 105 to the output opening 115may be controlled. The control may be through the use of a pump or avalve (113). In certain embodiments, no pump or valve exists between thereaction chamber 105 and the output opening 115.

As depicted in FIG. 1A, in certain embodiments, the holding chambers 101connect to the mixing chamber 103 via a single pipe, i.e., there is aT-junction before the mixing chamber 103. However, as depicted in FIG.1B, in certain other embodiments, each holding chamber 101 is separatelyconnected to the mixing chamber 103.

In some embodiments, the device of the present invention also features atemperature control unit. The temperature control unit controls thetemperature of the holding chambers 101, the mixing chamber 103, thereaction chamber 105, or a combination thereof, or the temperature ofthe entire device. These components may be held at room temperature, ata temperature above room temperature, or at a temperature below roomtemperature, depending on the reaction conditions and the needs of theparticular use contemplated. In some embodiments, different parts of thedevice are held at different temperatures, thus, requiring more than onetemperature control unit for the device.

In certain embodiments, the mixing chamber 103 may just be a pipe or ahose connecting the holding chambers 101 to the reaction chamber 105. Insome other embodiments, the reaction chamber 105 may just be a pipe or ahose connecting the mixing chamber 103 to the output opening 115.Therefore, in one embodiment of the invention, the entire device willcomprise of a pipe or a hose connecting the holding chambers 101 to theoutput opening 115.

B. Solid State Production Device

In another aspect, the invention relates to a device for continuouslysynthesizing ferrate, comprising a holding chamber; a mover controllablyconnected to the holding chamber such that at least a portion of acontent of the holding chamber is transferred to the mover; a heatingchamber, through which at least a portion of the mover moves; an outputopening in the heating chamber through which the content on the mover isadapted to be transported to a site of use, where the site of use isproximal to the heating chamber.

In certain embodiments, the mover comprises a conveyor belt. The belt ismade of materials that can withstand temperatures higher than roomtemperature. These materials may include, but not be limited to, rubber,steel, aluminum, glass, porcelain, etc.

Some of the embodiments of the invention relate to a device that furthercomprises a mixer between the holding chamber and the mover.

In other embodiments, the heating chamber further comprises atemperature control device.

Other embodiments of the invention relate to a device that furthercomprises a storage chamber after the output opening in the heatingchamber. Therefore, the conveyor belt may deposit the heated mixtureinto this storage chamber following the heating event.

One embodiment of the device of the present invention is depicted inFIG. 2. Starting materials are added to holding chambers 201. Someembodiments of the invention exhibit only one holding chamber 201, whileothers exhibit two or more holding chambers 201. The starting materialsare then combined and added to a belt 203 that carries the startingmaterials through a heating chamber 205. The starting materials may becombined prior to their placement on the belt 203, or may be mixed onthe belt 203 after they have been placed there separately.

The embodiment depicted in FIG. 2 shows that the holding chambers emptytheir contents into a single pipe which in turn empties the startingmaterial through opening 211 onto the belt 203. However, in otherembodiments, each holding chamber may separately empty its contents ontothe belt 203.

In some embodiments, the flow of material between the holding chambers201 and the belt 203 may be controlled. The flow is controlled either bythe presence of a pump or a valve (207) after each holding chamber 201,or by the presence of a pump or a valve (209) before the opening 211, orby a combination thereof. In certain embodiments, no pump or valveexists between the holding chamber 201 and the opening 211.

In certain embodiments, the starting materials are added directly ontothe belt 203. However, in other embodiments, the starting materials areadded into containers that are placed on the belt. Starting materialsmay be added into the containers before positioning the containers onthe belt, or the containers may be positioned on the belt before thestarting materials are added.

The heating chamber 205 comprises a heating unit that can heat thetemperature within to above room temperature. Various heating units areknown in the art. In FIG. 2, the heating chamber 205 is depicted as acylinder, though those of skill in the art realize that the heatingchamber may have any shape, such as a cube or a sphere or the like. Theheating unit 205 may also exhibit a temperature control unit.

The speed with which the belt travels through the heating unit, thelength of the heating unit, and the temperature of the heating unit canbe controlled by the operator in order to ensure that the necessaryyield of ferrate is achieved. Therefore, the device of the presentinvention may exhibit a quality control device at the exit end of theheating unit (213) that can determine the yield of ferrate in themixture. The quality control device may be a chemical sensor, aphotochemical sensor, a spectrophotometer, or the like. The qualitycontrol device may be connected to a computer that can control the speedof the belt through the heating unit and/or the temperature of theheating unit. Therefore, if the yield of ferrate is too low, the devicemay automatically decrease the speed of the belt and/or increase thetemperature of the heating unit. Similarly, if the yield of ferrate istoo high, the device may automatically increase the speed of the beltand/or decrease the temperature of the heating unit. In otherembodiments, the quality control device issues a signal to the operatorof the device, where the operator may manually adjust the speed of thebelt and/or the temperature of the heating unit.

At the exit end of the heating unit 213, ferrate is removed from thebelt 203 and is delivered to the site of use. In some embodiments,ferrate just falls off the belt 203 and into a receiving chamber 217,where it can be delivered to the site of use through the opening 215. Inother embodiments, where ferrate is in a container, the container isremoved from the belt and the contents thereof are emptied into thereceiving chamber, either manually or automatically.

After removing the ferrate from the belt 203, the belt 203 then loopsaround to receive more ferrate and repeat the process.

C. Electrochemical Production Device

In another aspect, the invention relates to a device for continuouslysynthesizing ferrate, comprising a reaction chamber comprising at leasttwo electrodes and a solution of an iron salt, where the electrodesprovide sufficient electric current to convert the solution of an ironsalt to a solution of ferrate; a holding chamber controllably connectedto the reaction chamber, into which the solution of ferrate is kept fora period of time; and an output opening in the holding chamber throughwhich the mixture is adapted to be transported to a site of use, wherethe site of use is proximal to the holding chamber.

In some embodiments the reaction chamber further comprises a mechanicalagitator.

In other embodiments the reaction chamber comprises a tube configured tomix the mixture as it passes through the tube.

In certain other embodiments the reaction chamber further comprises atemperature control device.

Some other embodiments of the invention further comprise a pumpdownstream from the reaction chamber and upstream from the holdingchamber. This pump controls the flow of material out of the reactionchamber and into the holding chamber.

In some of the embodiments of the invention the holding chambercomprises a tube located between the reaction chamber and the outputopening.

One embodiment of the device of the present invention is depicted inFIG. 3. The figure depicts a holding chamber 301. Other embodiments ofthe invention may exhibit additional holding chambers, depending on thenumber of ingredients added initially. Some embodiments of the inventionmay exhibit two or more holding chambers 301. The holding chamber isconnected to the reaction chamber 303. In some embodiments, the flow ofmaterial between the holding chamber 301 and the reaction chamber 303may be controlled by the presence of a pump or a valve (307) after theholding chamber 301. If there are more than one holding chambers 301,then the flow may be controlled either by the presence of a pump or avalve (307) after each holding chamber 301, or by the presence of a pumpor a valve before the reaction chamber 303, or by a combination thereof.In certain embodiments, no pump or valve exists between the holdingchamber 301 and the reaction chamber 303.

The reaction chamber 303 comprises at least two electrodes 321. Theelectrodes are connected via wires 319 to a power source 317. The powersource 317 may be an AC or a DC power source. The electrodes 321 and thepower generated by the power source 317 are such that they are able toelectrochemically oxidize iron, in any oxidation state below +4, toferrate. In some embodiments, one of the electrodes is an ironelectrode, which serves as both an electrode and as the source of ironfor the production of ferrate. If the electrode is an iron electrode,there may or may not be a need for having a holding chamber 301 in thedevice. An “iron electrode” includes any electrically conductingmaterial comprising iron.

The reaction chamber 303 is connected with an output opening 315,through which the product of the reaction is transferred to the site ofuse. The flow from the reaction chamber 303 to the output opening 315may be controlled. The control may be through the use of a pump or avalve (313). In certain embodiments, no pump or valve exists between thereaction chamber 303 and the output opening 315.

In certain embodiments, there is a second holding chamber 305 betweenthe reaction chamber 303 and the output opening 315. The second holdingchamber may serve as a storage place for the generated ferrate betweenthe time of its generation and the time of its use. The flow between thereaction chamber 303 and the second holding chamber 305 may becontrolled through the use of a pump or a valve (311).

In some embodiments, the device of the present invention also features atemperature control unit. The temperature control unit controls thetemperature of the holding chambers 301, the reaction chamber 303, thesecond holding chamber 305, or a combination thereof, or the temperatureof the entire device. These components may be held at room temperature,at a temperature above room temperature, or at a temperature below roomtemperature, depending on the reaction conditions and the needs of theparticular use contemplated.

IV. Purification/Separation of Ferrate

The ferrate produced by the methods of the present invention may be usedwithout substantial purification. By “substantial purification” it ismeant a purification step that brings the purity of the ferrate in thesolution to greater than 99%, that is, a substantially pure ferratesolution is a solution in which more than 99% of the solutes compriseferrate and its counter-ion.

However, the ferrate solution generated by the methods of the presentinvention may be somewhat purified or undergo a separation step. Forexample, the ferrate solution may be filtered to remove undissolvedsolids. The filtration may be physical filtration, in which particlesthat are too big to pass through the filter pores are removed, orsurface filtration, where the particles are captured on the surface offilter grains, or a combination of one or more filtration processes.

Ferrate may also be purified using ion exchange purification. In thisprocess, ferrate ions are reversibly bound to a solid state material,the column is purged of unwanted impurities, and then the ferrate isreleased from the column. The solid state material of the ion exchangecolumn may be any of the solid state materials currently used, ordesigned later, for this purpose, and include without limitation, clays,zeolites, phosphonates, titanates, heteropolyacid salts, layered doublehydroxides, inorganic resins, organic resins, and gel-type exchangers(e.g., as small beads in several mesh sizes), and carbon-based inorganicexchangers. Additionally, inorganics can be incorporated into organicresins to make composite exchangers for purifying ferrate.

Membranes used for purification of ferrate may be made of materials suchas organic polymeric materials. The membrane materials can be celluloseor polyamide (for example, fully aromatic polyamide TFC membranes).Other membranes include, but are not limited to, microfiltration,ultrafiltration, and inorganic nanofiltration membranes. These membranesare generally made from glass, ceramics, or carbon.

Ferrate may also be purified in a direct electric field technique,during which a direct current electric field is applied across a pair ofelectrodes. The ferrate ions in the liquid phase are moved under theaction of the field to a desired location where they are pumped out foruse. The ferrate transport under the action of an electric field can beelectromigration, electroosmosis, or electrophoresis.

The ferrate solution produced by the methods of the present inventionmay also be stored in a sedimentation tank for a period of time and thesupernatant then decanted or pumped out. The ferrate solution may alsopass through a centrifuge where the solution is spun such that theheavier particles in the solution sink to the bottom and thesupernatant, comprising purified ferrate, is removed for further use.

In certain other embodiments, the ferrate produced by the methods of thepresent invention is encapsulated in a membrane for future use. Themembrane may be molecular sieves, clay, porcelain, or other porousmaterial that are not susceptible to oxidation by ferrate. Then, to usethe ferrate, at least a portion of the membrane is contacted with theaqueous or gaseous mixture to be treated.

The membrane may also be slightly water soluble so that as portions ofit are dissolved away, more ferrate is exposed to the aqueous mixture tobe treated. In this embodiment, the use of ferrate may be in atime-release manner, the time of the release being defined by thesolubility of the layers of the membrane.

The devices disclosed herein may also feature a purification componentthat purifies ferrate consistent with the purification methods describedherein.

V. Uses of Ferrate

In another aspect, the invention relates to a method of treating, at asite of use, an aqueous mixture having one or more impurity, comprisingcontinuously generating ferrate in a reaction chamber located proximalto the site of use; contacting the ferrate with the aqueous mixture atthe site of use, whereby at least a portion of the impurity is oxidized.

In certain embodiments, the impurity is selected from the groupconsisting of a biological impurity, an organic impurity, an inorganicimpurity, a sulfur-containing impurity, a nitrogen-containing impurity,a metallic impurity, and a radioactive impurity, or a combinationthereof. Other impurities are as described herein.

An “impurity” is defined to be any component of a solution or a system,whose presence within that solution or system is repugnant to thecontemplated use of that solution or system. Biological impurities arethose that have a biological origin. Thus, any cells, bacteria, viruses,tissues, etc., or components thereof, whether from plants or animals,are considered to be biological impurities. Organic impurities arechemical compounds that contain at least one carbon atom. Inorganicimpurities are chemical compounds that contain no carbon atoms. Asulfur-containing impurity is one which contains at least one sulfuratom. A nitrogen-containing impurity is one which contains at least onenitrogen atom. A metallic impurity is one which contains at least onemetal atom, whether main group metal, transition metal, or f-blockmetal. A radioactive impurity is one which undergoes radioactive decay,whether by emitting α, β, or γ particles. Those of skill in the artrecognize that a particular impurity may fall within more than onecategory listed above. For example, calcium ethylenediaminetetra-acetate (EDTA) impurity in water is an organic impurity, anitrogen-containing impurity, and a metal-containing impurity.

The ferrate for use in the treatment method is produced by one of themethods set forth herein, i.e., the chemical production, the solid stateproduction, or the electrochemical production.

The ferrate produced by the above methods is contacted with the aqueousmixture to be treated. In some embodiments the contacting step comprisesadding the ferrate to a stream of the aqueous mixture. In otherembodiments, the contacting step comprises contacting the ferrate to apool of the aqueous mixture. In yet other embodiments the contactingstep comprises contacting a stream of the aqueous mixture with astationary container containing the ferrate.

Generally, the ferrate produced by the process of this invention can beused in connection with any known process and for any known purpose. Theferrate produced by the process of this invention is especially usefulas an oxidant, flocculent and/or coagulant. In particular, potentialuses of ferrate produced by the process of this invention include thefollowing: removal of color from industrial electrolytic baths;manufacture of catalysts for the Fischer-Tropsch process to producereduced hydrocarbons from carbon monoxide and hydrogen; purification ofhemicellulose; selective oxidation of alkenes, alkyl side chains,organic sulfur compounds, thiols, sulfinic acids, organic nitrogencompounds, carboxylic acids, halides, alcohols and aldehydes and inoxidative coupling; as a general oxidant for water, waste water andsewage treatment; disinfection as a biocide or virocide; phosphorylaseinactivator; anti-corrosion paint additive; denitration of flue gas;electrodes for batteries; detoxification of cyanide and thiocyanate fromwaste waters; oxygen demands measurement; cigarette filters to removeHNC and carcinogenic molecules; oxidizer for hazardous wastes and otherwaste solutions such as from the pulp industries; pollution control inthe removal of hydrogen sulfide from low pressure gas streams; removalof pollutants with mutagenic and carcinogenic characters such asnaphthalene, nitrobenzene, dichlorobenzene and trichloroethylene fromwaste water and drinking water without coproduction of harmful products;additive to cements as structural hardener; disinfectant to inactivateE. coli, Salmonella, Shigella, and other fecal coliform as a bacterialcell removal step; removing Streptococcus and Staphylococcus; biofoulingcontrol with non-corrosive oxidant for removal of slime films formed ofmicroorganisms such as in electric power plants and shipboard coolingsystems; removal of bacteria, heavy metals and inorganics in drinkingwater in an oxidation coagulation processes; removal of hydrogen sulfidefrom sour gas in the “Knox” process; delignification of agriculturalresidues to produce glucose and ethanol from wheat straw; magneticfiller of barium and strontium ferrate for flexible plastics having highpolymer binder contents; support for other oxidizers such as chromium(VI) and KMnO₄; denitrification of sinter furnace off-gas; removal ofimpurities from solutions fed to zinc plants; decontamination of wastewaters containing cyanide and thiocyanate; oxidative destruction ofphenol, sulfite and thiosulfate; as a catalyst in burning of coal toremove impurities in steam gasification step; component of grindingwheels; etching agent in fluid form for evaporated films; and ceramicencapsulated rare earth metal ferrates for use in electronics whereferromagnetic properties are needed. These and other applications arediscussed in Deininger, U.S. Pat. Nos. 5,202,108, 5,217,584, and5,370,857, all of which are incorporated herein by reference in theirentirety.

Additional uses of ferrate are discussed below.

A. Waste Water Treatment

As noted above, there is a need for development of safe, inexpensive and“environmentally friendly” oxidants, especially for water and wastewatertreatment applications. The treatment of industrial and municipaleffluents containing hazardous organic and inorganic compounds is animportant research endeavor. Currently, several methods for contaminantremoval exist, including adsorption, coagulation, biodegradation,chemical degradation, and photodegradation. Chemical degradation isoften the most economically feasible as well as the easiest method forwater treatment and usually involves chlorine, hypochlorite, or ozone.Although effective, these oxidants often have deleterious side effects.Chlorine and ozone are poisonous and highly corrosive gases.

Hypochlorite is generally supplied as a solid or in aqueous solution;however, it is generated using chlorine gas and can rapidly decomposeback into chlorine upon heating or chemical mishandling. Also, althoughhypochlorite, OCl⁻, is used as a chlorine source for water treatment atsmaller operations, it is expensive.

Additionally, the handling of chlorine, or hypochlorite, poses potentialdanger to workers due to its high toxicity. A major disadvantage ofchlorine and chlorine-containing oxidants is that excess chlorine canproduce chlorinated oxidation products (e.g., chloramines, chlorinatedaromatics, chlorinated amines or hydrocarbons), many of which arepotential mutagens or carcinogens, and may be more toxic than the parentcontaminants and/or more difficult to remove. Because these compoundspotentially constitute a health hazard for the public, a move away fromchlorine use is needed.

The ferrate produced by the methods of the present invention may be usedin treating waste water, sewage, or sludge. It is well known in the artthat ferrate reacts with organic or inorganic compounds and biologicalentities, such as cells, bacteria, viruses, etc. In this reaction, thesubstrates are oxidized to biologically inactive products. The ferratemolecule itself is reduced to Fe(III), which precipitates out of thesolution as Fe(OH)₃ or other Fe(III) salts. The iron containing saltscan be easily filtered out, leaving iron-free water containing innocuousby-products.

Escherichia coli, Salmonella, and Shigella are all members of theEnterobacteriaceae. These bacteria and certain others known to those ofskill in the art have similar physiological characteristics, includingbeing rod shaped gram-negative facultatively anaerobic organisms. E.coli has long been used as an indicator of fecal pollution in watersystems and there is a large volume of disinfection literature availablefor this particular organism. Ferrate is an effective biocidal agentagainst suspended bacterial cultures in clean systems. Ferrate has thecapacity to rapidly inactivate several known pathogens at fairly lowconcentrations.

Ferrate is also an effective disinfectant against viruses, such as theF2 virus. Ferrate has been studied for its antiviral activities and hasbeen found to be effective in inactivating viruses (Kazama, Wat. Sci.Tech. 31(5-6), 165-168 (1995).) Ferrate also coagulates turbidity inwater system and inactivates most enteric pathogens at ferrateconcentrations which are reasonable for use in a water and wastewatertreatment facility.

The biocidal properties of ferrate have also been investigated (Y.Yamamoto, Mizu Shori Gijutsu, Vol. 24, p, 929 (1983)). An importantproperty of ferrate toward its application as a water treatment agent isits ability to act as a potent biocide. Ferrate has been used fordisinfection in river water treatment, as well as in municipal sewagetreatment processes; with its use, removal of coliform bacteria dependson the pH. It has been shown to be effective against E. coli andsphaerotilus (F. Kazama, J. Ferment. Bioeng., Vol. 67, p.369 (1989)).Ferrate has also been used to remove coliform bacteria from treatedsewage and river water (F. Kazama and K. Kato, Hamanashi DaigakuKogakubu Kenkyu Hokoku, Vol. 35, p.117 (1984)).

In addition, ferrate can be used to oxidize ammonia in the secondaryeffluent from water treatment plants. The major oxidation product isnitrogen, while some nitrites are also present in the products. Both ofthese oxidation products are environmentally friendly.

The above properties of ferrate can be exploited at municipal orindustrial water treatment plants. A ferrate producing device can beinstalled in close proximity of the water treatment facility. Waste fromthe municipal sewer lines or the industrial effluent lines is mixed withfreshly produced ferrate on site. The ferrate producing device canproduce as much or as little ferrate as is necessary to react with allthe waste present in the effluent.

Since ferrate is an efficient disinfectant, it has potential for use inlieu of extensive chlorination of drinking water. As pollutionincreases, the need exists for a water purifying agent that can besafely used by the individual on “small” quantities of drinking water aswell as at the municipal/industrial wastewater level. Such purificationagents should ideally be able to disinfect and remove suspendedparticulate materials, heavy metals (including radioisotopes) and someorganics through flocculation, in order to at least partially destroydissolved organic contaminants through oxidation, and as a final step,to remove itself from solution. A one-step purification reagent whichmeets these criteria is FeO₄ ²⁻, ferrate. This ion is able tosuccessfully compete with the current two-step, chlorination/ferricsulfate, flocculation technique, thereby circumventing the production oftoxic or carcinogenic halogenated organics.

Since ferrate has multipurpose oxidant-coagulant properties, it is veryattractive for the treatment of waste produced by chemical andpharmaceutical companies. These companies spend billions of dollars ayear in clean up costs for contaminated water used, or produced, intheir processes. Almost all of the waste produced by these companies canbe oxidized to relatively harmless by-products by ferrate, leaving waterthat can be released to the municipal sewage systems and be treatedwithout any special care. Thus, any company that produces waste waterlaced with organic, inorganic, or biological impurities can install aferrate producing device at the end of its effluent line.

Municipal sewage systems suffer a special burden. They are overloadedwith any imaginable waste, most of which is organic or biological. Oncethe large objects are filtered out, the sewer facilities must deal withthe soluble waste remaining behind. Normally, waste water facilitiesfilter the waste water through activated charcoal or other filters thathave an affinity for organic compounds, or biologically treat thewastewater. These processes are slow and costly. The slow response ofthese facilities to the in-flow of wastewater often results in seweroverflows during storms. In coastal communities this results in raw anduntreated sewage spilling into the ocean or lake nearby, causingenvironmental damage. While oxidants may easily be used to remove theunwanted waste rapidly, the oxidants currently available on the marketare either cost prohibitive, or produce by-products that are at timesmore environmentally unsafe than the waste itself.

Also, there is a vital need for new methods for H₂S control in municipalsanitary sewer systems and treatment plants, and industrial wastetreatment facilities. One of the ongoing major problems in waste watertreatment is severe corrosion of facility structures from contact withhydrogen sulfide gas, H₂S, or its oxidation products after contact withair. Equally important are the health risks from exposure to H₂S gas foreven short periods of time; such exposure is reported to be the leadingcause of death among sanitary sewer workers. Another major problem withthe evolution of H₂S gas is its foul smell that causes discomfort tothose exposed to it.

Ferrate is known to be useful in a variety of waste water treatmentapplications. Ferrate oxidations, and their application to waste watertreatment, have been studied with a view toward using ferrates inseveral industrial applications, in particular with a number of organicand inorganic substrates. (J. D. Carr, P. B. Kelter, A. Tabatabai, D.Spichal, J. Erickson, and C. W. McLaughlin, Proceedings of theConference on Water Chlorination and Chemical Environmental ImpactHealth Effects, pp. 1285-88 (1985)). The applicability of ferrate inwaste treatment involves not only its oxidative abilities, but alsoother multipurpose properties, such as its floc formation, disinfectiveproperties, and generally remediative faculties.

Direct filtration of ground water using ferrate has been examined at thepilot plant level (T. Waite, Environ. Sci. Technol., Vol. 17, p.123(1983)). Biofouling control has been investigated (R. L. Bartzatt and D.Nagel, Arch. Env. Health, 1991, Vol. 46(5), pp. 313-14 (1991)). Thecoagulative properties of ferrate have been found to be useful forturbidity removal (S. J. de Luca, C. N. Idle, A. C. Chao, Wat. Sci.Tech. 33(3), 119-130 (1996)). Studies have shown that when modelcondensers were dosed with 10⁻⁵ M solutions of ferrate twice a day, for5 minutes, biofilm growth was inhibited (T. Waite, M. Gilbert, and C.Hare, Water Tech/Qual., pp. 495-497 (1976)).

Ferrate oxidative destruction of nitrosamines, which are potentcarcinogens, in waste water has been reported (D. Williams and J. Riley,Inorg. Chim. Acta, Vol. 8, p. 177 (1974)).

Relatively low ferrate doses have been found to profoundly reduce theBOD (biological oxygen demand) and TOC (total organic carbon) indomestic secondary effluents (F. Kazama and K. Kato, Kogabkubu KenkyuKokou, Vol. 35, pp. 117-22 (1984)).

Ferrate can be employed for the treatment of mill effluent and sewagesludge from municipal sources. Treatment at 125-1000 mg of K₂FeO₄/L doselevels was found to significantly decrease the chemical oxygen demand onmanganese (COD_(Mn)), due to partial oxidation of the high molecularweight organics. Decreases in the UV spectrum after treatment withferrate have been interpreted as removal of fulvic and humic acidswithin the iron(III) coagulate produced when the ferrate was reduced (F.Kazama and K. Kato, Kogabkubu Kenkyu Kokou, Vol. 34, pp. 100-4 (1984)).

Polyaminocarboxylates such as diethylenetriaminepentaacetate (DTPA),ethylenediaminetetracetate (EDTA), and nitriloacetate (NTA) aresynthetic ligands that form stable complexes with most of the metals andare used in a variety of industrial applications such as photographicdeveloping, paper production, and textile dyeing.Ethylenediaminedisuccinic acid (EDDS) forms hexadentate chelates withtransition metals and is used in consumer products, e.g., washingpowder. EDTA is a constituent of formulations for chemicaldecontamination of the primary heat transport system of nuclear powerreactors. The presence of heavy metals, along with polyaminocarboxylateshas been reported at many US Department of Energy (DOE) sites. Thesepolyaminocarboxylates are either poorly biodegradable (e.g., EDTA),associated with other safety regulatory issues (e.g., NTA) or littleeffective (e.g., citrate). Ferrate can be applied to degradepolyaminocarboxylates and metal-polyaminocarboxylates to simpleproducts.

Certain compounds are listed in the EPA Contaminant Candidate List(CCL). These include diazion, disulfoton, fonofos, terbufos, cyanazine,prometon, 1,2-diphenylhydrazine, nitrobenzene, acetochlor,2,4,6-trichlorophenol, and 2,4-dichlorophenol. These compounds can beoxidized by ferrate.

The gasoline additive methyl tert-butyl ether (MTBE) is a ubiquitousgroundwater contaminant. The U.S. geological Survey National WaterQuality Assessment Program has identified it in 27% of urban wellstested. A more recent survey indicated that between 5 and 10% of allcommunity drinking wells in the United States have detectable MTBEcontamination. It persists in petroleum-contaminated aquifers. MTBE ingroundwater can be oxidized to relatively non-hazardous compounds usingferrate.

Trichloroethene (TCE), a nonflammable solvent used in large quantitiesin industry, is one of the most common organic ground water contaminantsand is classified as a “probable human carcinogen.” TCE is sequentiallyreduced to dichloroethene (DCE) isomers, chloroethene (CE), and ethene.The use of ferrate in remediating contaminated groundwater is attractivedue to ease of field implementation and the relatively low cost.

Highly chlorinated phenol derivatives, such as pentachlorophenol (PCP)have been listed as a priority pollutant by the United StatesEnvironmental Protection Agency. PCP is mainly used as a woodpreservative and general biocide. PCP is a suspected carcinogen and itspyrolysis and combustion reaction products are considerably more toxicthan PCP itself. Ferrate can be utilized in degradation of PCP.

Ferrate can also be applied to effluent streams from agrochemicalindustry. One of the common products from an agricultural industry, theherbicide trifluaraline is a pre-emergent, cellular and nuclear divisioninhibitor. It is highly toxic for humans. Ferrate can be applied toeffluent streams of agrochemical industry containing compounds such astrifluraline.

Dyes present in wastewater, which originated from the textile industry,are of particular environmental concern since they give undesirablecolor to the waters. They are also generally harmful compounds and canlead to toxic byproducts through hydrolysis, partial oxidation, or otherchemical reactions taking place in the waste phase. The decolorizationand degradation of different classes of textile dyes from the textileindustry can be achieved using ferrate.

In pharmaceutical and fine chemical manufacturing, organictransformations are routinely carried out using oxidizing agents basedon transition metal compounds. One of the biggest problem areas insynthetic methodology is selective oxidations. For example, theoxidation of alcohols carried out with Cr(VI) or Mn(VII) lackspecificity and selectivity. Ferrate is selective and specific in thesereactions. The nontoxic properties of the Fe(III) byproduct makesferrate an environmentally safe oxidant. Ferrate can be utilized inorganic synthesis, thereby reducing the environmental impact of theoxidation processes and also reducing their cost (“green chemistry”).

Thiourea and its derivatives are known corrosion inhibitors and are usedas chemical complexing agents to clean scales developed in industrialequipment, like boilers and nuclear reactors. Because of the toxicity ofthiourea to aquatic organisms, the treatment of boiler chemical cleaningwastes (BCCWs) is required before their disposal. Ferrate can easilyremove thiourea and its derivatives from BCCWs.

Oil refineries and coke processing plants generate sulfur and cyanidecontaining compounds. These contaminants are toxic and environmentallysignificant due to their offensive odor. In addition, their presence maynot be acceptable in the environment due to their high oxygen demand.Ferrate can be applied to petroleum industry effluents to eliminate odorrelated to sulfur and cyanide containing compounds.

Drinking water supplies are sometimes plagued by odors resulting fromthe presence of manganese(II). Manganese(II) causes aesthetic problemssuch as colored water, turbidity, staining, and foul taste.Manganese(II) can also accelerate biological growth which furtherexacerbates odor problems. Mn(II) is removed by oxidation of solubleMn(II) with a ferrate to sparingly soluble hydroxide and oxide solidphases, MnOOH(s) and MnO₂(s), respectively.

Decontamination of chemical warfare agents is required on thebattlefield as well as in pilot plants, and chemical agents production,storage, and destruction sites. Ferrate can oxidize chemical warfareagents such as VX[O-ethyl-S-(2-diisopropylamino)ethylmethylphosphono-thioate], GD(pinacolyl methylphosphonofluoridate), GB(2-propylmethylphosphonofluridate), mustard gas (2,2′-dichlorodiethylsulfide), and HD [bis(2-chloroethyl) sulfide]. Ferrate has manyapplications such as environmentally friendly “hasty” decontamination onthe battlefield where speed and ease of application of the decontaminantis essential.

During recovery of natural gas and crude oil from offshore and onshoreproduction operations, produced waters are generated, containingcomplexed mixtures of organic and inorganic materials. Approximately, 12billion barrels of produced water are produced in the US annually. Thislarge volume causes major environmental problems. The water toxicity andorganic loading generally characterize the impact of produced water tothe environment. The treatment with ferrate can reduce the organicloading and acute toxicity of the oil field produced water.

Water supplies containing arsenic compounds are a worldwide healthconcern. Tens of thousands of people already show symptoms of arsenicpoisoning. A maximum of ten microgram/L of arsenic in water is thethreshold value recommended by the World Health Organization and theEuropean Community. Current removal procedures are not adequate to meetcriteria for ambient arsenic in water supplies. Steps involvingoxidation, adsorption, and precipitation can be carried out by ferratein removing arsenic from water.

In recent years, there has been increasing concern for the presence ofnatural organic matter (NOM) in potable surface and ground watersupplies. One reason for concern is related to the formation ofdisinfection byproducts (DPB's) from the treatment of water bychlorination methods. Oxidation of NOM by chlorination produceschlorinated hydrocarbons, many of which are known or suspectedcarcinogens. Ferrate has excellent potential to serve as anenvironmentally friendly remediation treatment for reducing levels ofDPB's in drinking water. This process would not form toxic chlorinatedorganics and may also effectively mineralize NOM to carbon dioxide,potentially eliminating the production of DPB's entirely.

Ferrate solution can be used to develop a method for protecting iron andsteel castings from corrosion. This procedure is based on the formationof ferric oxide from the decay of the thin film of ferrate on the metal.In this procedure, a mixture of alkaline metal ferrate and alkalinesolution containing a reducing agent is brought into contact with metalsurfaces.

There are several disadvantages of using metal salts such as alum,ferric chloride, and ferrous sulfate in removing solids from a solution.First, binding of water to the metal ions creates a gelatinous sludgewith a high water content that increases dewatering costs. Second, thewater becomes more acidic after the addition of salts, causing adecrease in the coagulant property of the salt. Thirdly, the formationof metal-phosphate complexes causes phosphate levels in the solution todecrease and, as a result, phosphate becomes less available to bacteria.This upsets the biological function of the system. Synthetic organicpolymers are used as common coagulants and flocculents to replace metalsalts. To achieve this end, a large quantity of polymer is required,which makes the process expensive. There are also several disadvantagesto using a synthetic polymer. Synthetic polymers release toxic materialsinto water due to solubility of polymers. In addition, solubility isalso greatly influenced by environmental factors such as temperature andpH. Polymers are very sensitive to the quality of water and also havelittle effect on BOD. A combination of polymers and ferrate can beadvantageous. This combination can require less amount of coagulant andthus be cost-effective. Polymer-ferrate complexes can be formed toeliminate the toxicity from the solubility of polymers. Polymer-ferratecomplexes can also have multi-purpose properties and can be lesssensitive towards quality of water.

A ferrate producing device located at a waste water facility will beuseful in overcoming all of the above-described problems faced by thesefacilities. The device of the present invention can produce inexpensiveferrate rapidly. Ferrate can be injected into the flow of waste waterand mixed therewith, thereby oxidizing and removing the unwanted waste.Ferrate oxidation of organic and inorganic compounds results inenvironmentally safe by-products. In addition, the iron containing saltby-products can easily be filtered off and removed from the waste water.This eliminates the need to repeatedly pass waste water through filters,activated charcoal, or geological reactors, or incubating the wastewater in pools of anaerobic bacteria for digestion of the organic waste.

The on-site generation of ferrate removes two of the problems associatedwith its use today: cost and instability. Because ferrate is produced onsite and can be applied immediately after its production, little or noattention must be paid to the fact that it is unstable. The ferrate issimply introduced into the waste water before it has had a chance todecompose. In addition, the application of ferrate requires no need forpurification, crystallization, or storage; therefore, the cost of itsuse is very low. Furthermore, the ferrate produced by the device of theinvention requires lesser amounts of expensive feed stock.

B. Treatment of Recreational Water

The ferrate generated by the methods of the present invention can beused in pool and spa applications. It is well known that pools,Jacuzzis, and spas become polluted with organic waste. The waste entersthe water from the body of the swimmers or by wind or insects. If leftuntreated, the water becomes turbid and foul. Usual methods of treatmentinclude the addition of oxidants such as bleach and anti-bacterial oranti-fungal agents. These treatments create unwanted side-effects. Theoxidants that are left in the water have an adverse effect on the skinof the swimmers using the water. In addition, the oxidants createenvironmentally harmful by-products, such as chlorinated hydrocarbons.

The device of the present invention can be fitted to any swimming poolor Jacuzzi such that the ferrate produced by the device is mixed withthe water in a mixing chamber, whereby all the organic waste is oxidizedto innocuous products, the iron salts are filtered away, and the cleanwater is re-introduced into the pool. This represents a highly effectiveand cost-efficient method of cleaning the pool water, since ferrateproduced by the methods of the present invention is less costly in thelong run than purchasing the numerous oxidants and anti-fungal chemicalsnecessary to treat a pool.

C. Use in Processing Plants

Many processing plants generate aqueous streams comprising biosolidssuch as proteins, carbohydrates, fats, and oils which must be treated toremove the potentially valuable biosolids products before the stream canbe discharged from the plant. These aqueous streams are often derivedfrom food processing plants and have solids contents of about 0.01% to5% on a weight basis. This invention provides a process forclarification of such streams, whereby the solids are flocculated, andbiosolids are optionally separated from the solids. The biosolids cansubsequently be used, for example, in animal feeds.

As defined herein, to “flocculate” means to separate suspendedbiosolidsfrom a stream comprising biosolids, where the biosolids becomeaggregated and separate to the top or bottom of the stream in which thebiosolids had previously been suspended. Flocculation produces aflocculated material, which, if desired, can be physically separatedfrom the stream. In the present invention, it is desirable to maximizethe size of the flocculated material in order to facilitate removal ofthis material from the stream.

The process of this invention involves treating an aqueous streamcomprising biosolids by contacting the stream with ferrate. The aqueousstream can be derived from any number of processes, which generate suchstreams, such as from animal and vegetable processing, includingprocessing for non-food uses.

In the process of this invention, the aqueous stream to be treated canbe from any processing plant that produces an aqueous stream comprisingbiosolids, such as food processing plants. For example, animalslaughterhouses and animal processing plants and other food processingplants may produce aqueous streams comprising protein, fats and oil.Animal slaughterhouses and processing plants include those for cattle,hogs, poultry and seafood. Other food processing plants include plantsfor vegetable, grain and dairy food processing plants for processingsoybeans, rice, barley, cheese, and whey; plants for wet-milling ofstarches and grains; as well as breweries, distilleries and wineries.Biosolids present in aqueous streams from these processes may includesugars, starches and other carbohydrates in addition to protein, fats,and oils. For example in processing soybeans, proteins are extractedinto an aqueous stream from which they are subsequently recovered. Thepresent invention is especially useful for treating streams from animalprocessing, and more particularly, from poultry processing.

While this invention is useful in conventional food processingoperations, which produce aqueous suspensions of biosolids, it should berecognized that this invention is also useful in treatment of aqueoussuspensions of biosolids derived from processing of food (animal orvegetable) materials, which may have non-food end uses. For example,when separated and recovered, proteins are useful in certain cosmeticsand other skin care formulations; starch has numerous non-food uses,including uses in paper manufacture. Further still, this invention isuseful to treat in general, any aqueous stream comprising biosolids,which may result from non-food processing operations. Moreover, thoughthe biosolids, as disclosed above, are generally suspended in asubstantially aqueous stream, the concentration of biosolids dissolvedin the stream depends on the properties of the stream or the biosolidssuch as, for example, pH, salinity, or other parameters.

The process of this invention involves treatment of an aqueous streamcontaining biosolids, for example, proteins, to reduce suspended solids(as measured by turbidity) and optionally to separate the biosolids. Thebiosolids can be recovered for subsequent use. It should be recognizedthat this process can capture both suspended biosolids as well assoluble materials, such as those present in blood and sugars.

The flocculated biosolids can optionally be separated from the treatedstream by conventional separation processes such as sedimentation,floatation, filtering, centrifugation, decantation, or combinations ofsuch processes. The separated biosolids can subsequently be recoveredand used in numerous applications. It has also been surprisingly foundthat the recovered biosolids from this process have reduced odor whendry relative to those recovered from a process using ferric chloride aspart of a flocculating system. The flocculated biosolids can beseparated and recovered by known techniques, such as those mentionedabove.

E. Use in Radioactive Clean Up

The process of the present invention is also useful for theprecipitation of radioactive materials, particularly uranium, dissolvedin aqueous solutions. The dissolved radioactive materials may be from anaturally flowing stream, or a uranium mining operation water treatmentplant. The water from the stream is destined to be treated by aconventional city water treatment facility for drinking and home use.

Ferrate has been proposed as a treatment agent for the removal ofradionuclides (transuranics) from waste water. To date, the focus hasbeen on the nuclear industry, where ferrate is used to remove uraniumand transuranic elements from contaminated water. In addition, there iscurrently an interest in using ferrate in the removal of plutonium andamericium from waste water effluent.

U.S. Pat. No. 4,983,306 to Deininger discloses a method for transuranicelement polishing from radioactive wastewater using FeO₄ ²⁻ thatinvolves adjusting the pH of a transuranic element-containing watersource to a range of 6.5-14.0. Supposedly, removal occurs byco-precipitation of the transuranics within the ferric hydroxide matrixsimilar to other heavy metals. Also, small amounts of a chemical areused compared to common technology. Based on chemical dosages,radioactive sludge generation using this method is reduced by 3-20%,depending on the suspended solids content in the wastewater feed(Deininger, et al., Waste Manage. '90, vol. 1, pp. 789-795 (1990)).

F. Use in Surface Cleaning

Dilute solutions of ferrate can be used for oxidizing pretreatment ofchromium (III) oxide containing films, resulting from corrosion of basemetal surfaces of piping systems and the like, to render the corrosionfilms more amenable to conventional chemical cleaning treatments. Thereis an existing need for replacement of currently used laboratoryoxidants, especially the chromate derivatives. Chromate and chlorine areof environmental concern, and in chromate oxidations, Cr(III) is formed,which is a suspected carcinogen. Also, in permanganate reactions, MnO₂is generated.

Removal of heavy metals, such as Cu, Cd, and Mn using ferrate is alsoknown. Ferrate has been shown to remove colloidal suspensions and heavymetals through flocculation (T. Suzuki, Odaku Kenkyu, Vol. 11 (5), p.293-296 (1988)). The mechanism for Mn removal involves the oxidativeformation of insoluble MnO₂ and subsequent entrapment of these metalsinto the Fe(OH)₃ precipitate resulting from ferrate's reduction product.Cu and Cd are removed in a similar manner. The removal of heavy metalions and humic acid by coagulation after treatment with potassiumferrate has been studied. Metal ions are generally trapped duringsedimentation (F. Kazama and K. Kato, Kogyo Yosui, Vol. 357, p. 8-13(Chemical Abstract 110:63421y) (1988)).

Additionally, metallic surfaces, such as those used in medical devicesor in the semi-conductor industry, need to be cleaned or disinfected.Current methods for cleaning metal surfaces require their exposure todisinfectants, such as bleach, that are highly corrosive. Consequently,the metal parts corrode and routinely fail due to fatigue and need to bereplaced. Aside from the high cost of replacing the corroded metalpieces, the failure of the instruments create discomfort and annoyancefor the users and liabilities for the manufacturers.

Ferrate produced by the methods of the present invention can be used toclean the surfaces of these metal parts. Ferrate is not corrosive anddoes not damage the integrity of the metal piece. As mentioned above,the biocidal activity of ferrate is comparable to that of bleach.Therefore, ferrate provides an efficient, effective, and economicalmeans by which these metal surfaces can be cleaned.

G. Medical Uses

In the medical arts, there is a great need to disinfect and cleaninstruments and surfaces. The ferrate generating device of the presentinvention can be used in a hospital setting for such a use.

In certain other embodiments, the ferrate generated by the methods ofthe present invention may be used to treat a wound, as described in U.S.Pat. No. 6,187,347, which is incorporated herein by reference in itsentirety.

VI. Some Embodiments of the Invention

Some of the embodiments of the invention refer to the following:

A method of continuously synthesizing ferrate, comprising:

a) mixing an aqueous solution comprising an iron salt and an oxidizingagent in a mixing chamber;

b) delivering at least a portion of the aqueous solution to a reactionchamber;

c) continuously generating ferrate in the reaction chamber;

d) delivering at least a portion of the ferrate to a site of use that isproximal to the reaction chamber; and

e) adding additional aqueous solution to the mixing chamber.

The above method, where the additional aqueous solution in step (e) isadded in an amount to substantially replace the portion of the aqueoussolution delivered to the reaction chamber.

The above method, further comprising adding a base to the aqueoussolution.

The above method, where the base comprises an ion selected from thegroup consisting of a nitrogen base, the hydroxide ion, the oxide ion,and the carbonate ion, or a combination thereof.

The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

The above method, where the oxidizing agent comprises at least one ofthe following: a hypohalite ion, a halite ion, a halate ion, a perhalateion, ozone, OXONE®, halogen, a peroxide, a peracid, a salt of a peracid,and Caro's acid, or a combination thereof.

The above method, where the oxidizing agent comprises a hypohalite ionselected from the group consisting of the hypochlorite ion, thehypobromite ion, and the hypoiodite ion.

The above method, where the oxidizing agent comprises a halite ionselected from the group consisting of the chlorite ion, the bromite ion,and the iodite ion.

The above method, where the oxidizing agent comprises a halate ionselected from the group consisting of the chlorate ion, the bromate ion,and the iodate ion.

The above method, where the oxidizing agent comprises a perhalate ionselected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

The above method, additionally comprising repeating steps (b) through(d).

A method of treating, at a site of use, an aqueous mixture having atleast one impurity, comprising

a) continuously generating ferrate in a reaction chamber locatedproximal to the site of use;

b) contacting the ferrate with the aqueous mixture at the site of use,whereby at least a portion of the impurity is oxidized.

The above method, where the impurity is selected from the groupconsisting of a biological impurity, an organic impurity, an inorganicimpurity, a sulfur-containing impurity, a metallic impurity, and aradioactive impurity, or a combination thereof.

The above method, where the step of continuously generating ferratecomprises the steps of:

a) mixing an aqueous solution comprising an iron salt and an oxidizingagent in a mixing chamber;

b) delivering at least a portion of the aqueous solution to a reactionchamber;

c) continuously generating ferrate in the reaction chamber;

d) delivering at least a portion of the ferrate to a site of use that isproximal to the reaction chamber; and

e) adding additional aqueous solution to the mixing chamber.

The above method, where the additional aqueous solution added in step(e) is in an amount to substantially replace the portion of the aqueoussolution delivered to the reaction chamber.

The above method, further comprising adding a base to the aqueoussolution.

The above method, where the base comprises an ion selected from thegroup consisting of the hydroxide ion, the oxide ion, and the carbonateion, or a combination thereof.

The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

The above method, where the oxidizing agent comprises a componentselected from the group consisting of a hypohalite ion, a halite ion, ahalate ion, a perhalate ion, ozone, OXONE®, halogen, a peroxide, aperacid, a salt of a peracid, and Caro's acid, or a combination thereof.

The above method, where the oxidizing agent comprises a hypohalite ionselected from the group consisting of the hypochlorite ion, thehypobromite ion, and the hypoiodite ion.

The above method, where the oxidizing agent comprises a halite ionselected from the group consisting of the chlorite ion, the bromite ion,and the iodite ion.

The above method, where the oxidizing agent comprises a halate ionselected from the group consisting of the chlorate ion, the bromate ion,and the iodate ion.

The above method, where the oxidizing agent comprises a perhalate ionselected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

The above method, where the contacting step comprises adding the ferrateto a stream of the aqueous mixture.

The above method, where the contacting step comprises contacting theferrate to a pool of the aqueous mixture.

The above method, where the contacting step comprises contacting astream of the aqueous mixture with a stationary container containing theferrate.

The above method, additionally comprising repeating steps (b) through

A device for continuously synthesizing ferrate for delivery to a site ofuse, comprising:

a) a first holding chamber;

b) a second holding chamber;

c) a mixing chamber controllably connected to the first holding chamberand to the second holding chamber, into which a content of the firstholding chamber and a content of a second holding chamber are added toform a first mixture;

d) a reaction chamber controllably connected to the mixing chamber, thereaction chamber adapted to receive the first mixture and maintain thefirst mixture for a period of time;

e) a ferrate mixture in the reaction chamber; and

f) an output opening in the reaction chamber through which the ferratemixture is adapted to be transported to the site of use,

where the site of use is proximal to the reaction chamber.

The above device, where the mixing chamber further comprises amechanical agitator.

The above device, where the mixing chamber comprises a tube configuredto mix the mixture as it passes through the tube.

The above device, where the mixing chamber further comprises atemperature control device.

The above device, further comprising a pump downstream from the firstand the second holding chambers and upstream from the mixing chamber.

The above device, further comprising a pump downstream from the mixingchamber and upstream from the reaction chamber.

The above device, where the reaction chamber comprises a tube locatedbetween the mixing chamber and the output opening.

A system for continuously synthesizing ferrate, comprising:

a) a first holding chamber containing an iron salt;

b) a second holding chamber containing an oxidizing agent;

c) a mixing chamber controllably connected to the first holding chamberand to the second holding chamber, into which the iron salt and theoxidizing agent are controllably added to form a mixture;

d) a reaction chamber controllably connected to the mixing chamber, intowhich the mixture is kept for a period of time, and in which ferrate issynthesized, and

e) an output opening in the reaction chamber through which the ferrateis adapted to be transported to a proximal site of use.

The above system, further comprising adding a base to the mixture.

The above system, where the base comprises an ion selected from thegroup consisting of the hydroxide ion, the oxide ion, and the carbonateion, or a combination thereof.

The above system, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

The above system, where the oxidizing agent comprises a componentselected from the group consisting of a hypohalite ion, a halite ion, ahalate ion, a perhalate ion, ozone, OXONE®, halogen, a peroxide, aperacid, a salt of a peracid, and Caro's acid, or a combination thereof.

The above system, where the oxidizing agent comprises a hypohalite ionselected from the group consisting of the hypochlorite ion, thehypobromite ion, and the hypoiodite ion.

The above system, where the oxidizing agent comprises a halite ionselected from the group consisting of the chlorite ion, the bromite ion,and the iodite ion.

The above system, where the oxidizing agent comprises a halate ionselected from the group consisting of the chlorate ion, the bromate ion,and the iodate ion.

The above system, where the oxidizing agent comprises a perhalate ionselected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

The above system, where the mixing chamber further comprises amechanical agitator.

The above system, where the mixing chamber comprises a tube configuredto mix the mixture as it passes through the tube.

The above system, where the mixing chamber further comprises atemperature control device.

The above system, further comprising a pump downstream from the firstand the second holding chambers and upstream from the mixing chamber.

The above system, further comprising a pump downstream from the mixingchamber and upstream from the reaction chamber.

The above system, where the reaction chamber comprises a tube locatedbetween the mixing chamber and the output opening.

A method of purifying drinking water comprising contacting ferrategenerated by the above methods with the drinking water, where thecontacting is at a site proximal to the generation site.

A method of purifying waste water comprising contacting ferrategenerated by the above methods with the waste water, where thecontacting is at a site proximal to the generation site.

A method of purifying sewage comprising contacting ferrate generated bythe above methods with the sewage, where the contacting is at a siteproximal to the generation site.

A method of cleaning surgical instruments comprising contacting ferrategenerated by the above methods with the surgical instruments, where thecontacting is at a site proximal to the generation site.

A method of removing radioactive materials from an aqueous solutioncomprising contacting ferrate generated by the above methods with theaqueous solution, where the contacting is at a site proximal to thegeneration site.

A method of cleaning a metallic or a polymer surface comprisingcontacting ferrate generated by the above methods with the metallic or apolymer surface, where the contacting is at a site proximal to thegeneration site.

A method of coating a metallic or a polymer surface comprisingcontacting ferrate generated by the above methods with the metallic or apolymer surface, where the contacting is at a site proximal to thegeneration site.

A method of continuously synthesizing ferrate, comprising:

a) providing a mixture of an iron salt and an oxidizing agent;

b) continuously delivering at least a portion of the mixture to aheating chamber;

c) exposing the mixture to elevated temperatures in the heating chamber,thereby generating ferrate;

d) removing at least a portion of the ferrate generated in step c) fromthe heating chamber;

e) adding additional mixture to the heating chamber.

The above method, where the additional mixture added to the heatingchamber is in an amount to substantially replace the portion of theferrate removed from the heating chamber.

The above method, further comprising adding a base to the mixture.

The above method, where the base comprises an ion selected from thegroup consisting of a nitrogen base, the hydroxide ion, the oxide ion,and the carbonate ion, or a combination thereof.

The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

The above method, where the oxidizing agent comprises a componentselected from the group consisting of a hypohalite ion, a halite ion, ahalate ion, a perhalate ion, halogen, a peroxide, a peracid, a salt of aperacid, and Caro's acid, or a combination thereof.

The above method, where the oxidizing agent comprises a hypohalite ionselected from the group consisting of the hypochlorite ion, thehypobromite ion, and the hypoiodite ion.

The above method, where the oxidizing agent comprises a halite ionselected from the group consisting of the chlorite ion, the bromite ion,and the iodite ion.

The above method, where the oxidizing agent comprises a halate ionselected from the group consisting of the chlorate ion, the bromate ion,and the iodate ion.

The above method, where the oxidizing agent comprises a perhalate ionselected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

The above method, where the mixture exposed to elevated temperature is asolid.

A device for continuously synthesizing ferrate, comprising:

a) a holding chamber;

b) a mover controllably connected to the holding chamber such that atleast a portion of a content of the holding chamber is transferred tothe mover;

c) a heating chamber, through which at least a portion of the movermoves;

d) an output opening in the heating chamber through which the content onthe mover is adapted to be transported to a site of use,

where the site of use is proximal to the heating chamber.

The above device, where the mover comprises a conveyor belt.

The above device, further comprising a mixer between the holding chamberand the mover.

The above device, where the heating chamber further comprises atemperature control device.

The above device, further comprising a storage chamber after the outputopening in the heating chamber.

A device for continuously synthesizing ferrate, comprising:

a) a reaction chamber comprising two electrodes and a solution of aniron salt, where the electrodes provide sufficient electric current toconvert the solution of an iron salt to a solution of ferrate;

b) a holding chamber controllably connected to the reaction chamber,into which the solution of ferrate is kept for a period of time; and

c) an output opening in the holding chamber through which the mixture isadapted to be transported to a site of use,

where the site of use is proximal to the holding chamber.

The above device, where the reaction chamber further comprises amechanical agitator.

The above device, where the reaction chamber comprises a tube configuredto mix the mixture as it passes through the tube.

The above device, where the reaction chamber further comprises atemperature control device.

The above device, further comprising a pump downstream from the firstand the second holding chambers and upstream from the reaction chamber.

The above device, further comprising a pump downstream from the reactionchamber and upstream from the holding chamber.

The above device, where the holding chamber comprises a tube locatedbetween the reaction chamber and the output opening.

A method of continuously synthesizing ferrate, comprising:

a) continuously providing an aqueous solution comprising an iron salt ina reaction chamber, where the reaction chamber comprises at least twoelectrodes;

b) providing sufficient electric current to the at least two electrodesto convert at least a portion of the iron salt to ferrate;

c) delivering at least a portion of the ferrate to a site of use that isproximal to the reaction chamber; and

d) adding additional aqueous solution to the reaction chamber.

The above method, where the additional aqueous solution added in step(d) is in an amount sufficient to substantially replace the portion ofthe aqueous solution delivered to the reaction chamber.

The above method, further comprising adding a base to the aqueoussolution.

The above method, further comprising adding an acid to the aqueoussolution.

The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

A method of synthesizing ferrate, comprising:

a) mixing an aqueous solution comprising an iron salt and an oxidizingagent in a mixing chamber to form a solution of ferrate;

b) delivering at least a portion of the solution of ferrate to a site ofuse that is proximal to the mixing chamber.

The above method, further comprising adding a base to the aqueoussolution.

The above method, where the base comprises an ion selected from thegroup consisting of a nitrogen base, the hydroxide ion, the oxide ion,and the carbonate ion, or a combination thereof.

The above method, where the iron salt is selected from the groupconsisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrouschloride, ferric bromide, ferrous bromide, ferric sulfate, ferroussulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferroushydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate,ferrous hydrogen carbonate, ferric carbonate, and ferrous carbonate, ora combination thereof.

The above method, where the oxidizing agent comprises a componentselected from the group consisting of a hypohalite ion, a halite ion, ahalate ion, a perhalate ion, ozone, OXONE®, halogen, a peroxide, aperacid, a salt of a peracid, and Caro's acid, or a combination thereof.

The above method, where the oxidizing agent comprises a hypohalite ionselected from the group consisting of the hypochlorite ion, thehypobromite ion, and the hypoiodite ion.

The above method, where the oxidizing agent comprises a halite ionselected from the group consisting of the chlorite ion, the bromite ion,and the iodite ion.

The above method, where the oxidizing agent comprises a halate ionselected from the group consisting of the chlorate ion, the bromate ion,and the iodate ion.

The above method, where the oxidizing agent comprises a perhalate ionselected from the group consisting of the perchlorate ion, theperbromate ion, and the periodate ion.

A method of treating, at a site of use, an aqueous mixture having atleast one impurity, comprising

a) continuously generating ferrate in a reaction chamber locatedproximal to the site of use;

b) contacting the ferrate with the aqueous mixture at the site of use,

whereby at least a portion of the impurity is coagulated.

EXAMPLES Example 1

Preparation of Ferrate(VI)

The following is one representative embodiment of a laboratory procedurefor synthesizing ferrate. Add 75 mL distilled water to a 250 mL beaker.Add 30 g of NaOH to result in a 10 M solution. Cool the caustic solutionin an ice bath. Pump Cl₂(g) (approximately 6.5 g) into the solutionwhile mixing. Add a second batch (70 g) of NaOH to the hypochloritesolution. Keep the solution cool. Coarse filter the precipitated saltresidue. Add 25 g of Fe(NO₃)₃.9H₂O while stirring. Filter through mediumcoarse filter. Analyze the Fe⁶⁺ yield using UV-Vis spectroscopy byobserving absorbance at about 510 nm.

Example 2

Synthesis and Measurement of Ferrate

Ferrate is synthesized using the procedure of Example 1, except 16.35 gof chlorine was used instead of 6.5 g, and 25 g NaOH is used as thesecond caustic addition instead of 70 g. 40 g ofcoarse-glass-frit-filtered caustic/hypochlorite solution is added to a50 mL jacketed reaction vessel containing a TEFLON®-coated magneticstirring bar. Controlled temperature water is circulated through thejacket to control and establish the reaction temperature. 5.0 g offerric nitrate nonahydrate (Fe(NO₃)₃.9H₂O ) is added over a period of afew minutes to begin the experiment.

Temperature is set at 30° C. Fraction Actual Actual Expected Observed ofIron Reaction Time, Wt*, Absorb- Absorb- in (VI) Tempera- min (g) ance†ance State ture, ° C. Notes 0 22.4 Begin iron addition 2 27 Completeiron addition 2.5 30 3.5 33.9 Beginning of reaction noted 5 0.33 1.040.25 0.24 31.1 10 0.32 1.01 0.40 0.40 30.7 17 0.31 0.98 0.48 0.49 30.425 0.33 1.04 0.59 0.57 30.4 35 0.32 1.01 0.60 0.59 30.3 45 0.34 1.080.695 0.64 30.5 *Actual Wt: For the spectrophotometric analysis, analiquot of the reaction solution is taken gravimetrically and dilutedwith pH 10 buffer. This is the weight of the aliquot. The dilution is to100 g. The pH 10 buffer solution is prepared by combining 10.0 g sodiumphosphate, dibasic and 0.71 g of a 40 g/L sodium borate solution withenough distilled water to make one liter of buffer solution. †ExpectedAbsorbance: “Expected Absorbance” refers to the theoretical absorbanceof the solution if all of the iron in the solution had been converted toFe(VI). The weight of the aliquot represents a fraction of the totalamount of iron in the experiment. If all of this iron is present asferrate, this is the computed absorbance value of the solution. Incombination with the observed absorbance, the computed resultfacilitates determination of the fraction of iron # in the +6 state.

The concentration of Fe(VI) is measured by the absorbance (A) of abuffered sample of the reaction product solution, relative to the blankpH 10 buffer solution, with a UV-Vis spectrophotometer set at awavelength of 510 nm. The formula for the fraction of iron converted toFe(VI) is as follows:${{fraction}\quad {converted}} = \frac{A \times 100 \times {RSW} \times {MWIS}}{{MAC} \times 1000 \times {SW} \times {wt}\quad I\quad \sin \quad R}$

where

A=absorbance measurement

RSW=the reaction solution weight (total weight in grams)

SW=the sample weight of the reaction solution taken to combine with49.7-49.85 g buffer solution (about 0.3-0.15 g, respectively)

MWIS=molecular weight of the iron source

wtISinR=weight of iron source used in reaction (in grams)

100=volume of buffer solution in cc's

1000=volumetric conversion factor for cc/L

MAC=molar absorptivity coefficient, which is equal to 1150/Mcm forFe(VI) in the pH 10 buffer solution at 510 nm

A=MAC×p×c

p=path length of the absorbance cell (cm)

c=concentration of Fe(VI) in g-moles per liter

Temperature is set at 35° C. Fraction Actual Actual Expected Observed ofIron Reaction Time, Wt, Absorb- Absorb- in (VI) Tempera- min gm anceance State ture, ° C. Notes 0 24 Begin iron addition 2 28.6 Completeiron addition 2.5 32 3.5 37 Beginning of reaction noted 5 0.32 0.2851.01 0.28 36 10 0.34 0.52 1.08 0.48 35.4 17 0.34 0.61 1.08 0.56 35.3 250.34 0.67 1.08 0.62 35.3 35 0.31 0.68 0.98 0.69 35.3 45 0.34 0.813 1.080.75 35.3 60 0.43 1.11 1.36 0.82 35.2

This example shows that, under the given conditions, maximum conversionof Fe(III) and maximum yield of Fe(VI) requires at least 60 minutes ofreaction time; and that Fe(VI) formation, in this case, is enhanced at35° C. over that obtained at 30° C.

Example 3

Preparation of Ferrate(VI)

Ferrate is synthesized using the procedure of Example 1, except 13 g ofchlorine was used instead of 6.5 g, and 25 g NaOH is used as the secondcaustic addition instead of 70 g. Reaction vessel is a jacketed beakermaintained at 35° C. Begin with 20 g of caustic/hypochlorite solution.Gradually add 1.6 g of ferric nitrate nonahydrate crystals. This is a 5fold stoichiometric excess of hypochlorite over ferric(III). The maximumtemperature achieved during this step was 39° C.

Actual Fraction of Actual re- Time, weight, Expected Actual Iron in theaction temp- min gm absorbance absorbance (VI) state erature, ° C. 150.3233 1.36 0.86 0.63 35.2 30 0.3427 1.44 1.14 0.79 35.2 45 0.2984 1.261.10 0.87 35.2 60 0.3289 1.39 1.25 0.90 35.2

This example shows that, compared with Example 2, the Fe(VI) yield isincreased by using more excess hypochlorite and caustic solutionrelative to the Fe(III) content of the reaction mixture. In thisexample, the volume of pH 10 buffer solution used was 50 cc instead of100 cc.

Example 4

Ferrate(VI) Decay Rates

Ferrate(VI) is synthesized and measured according to the procedures ofExamples 1 and 2, except that the following reactant quantities areused:

Experiment Fe(NO₃)₃ 9H₂O (g) NaOH (g) Cl₂ (g) A 6.01 13.6 3.24 B 4.1913.6 3.47 C 2.41 13.6 3.24

In each case, the jacketed reaction vessel temperature is controlled at35° C. for about the first 2 hours and then allowed to slowly cool toambient conditions (about 23° C.

Experiment A Experiment B Experiment C Reaction Fraction ReactionFraction Reaction Fraction Time of Fe in Time of Fe in Time of Fe in(min.) (VI) State (min.) (VI) State (min.) (VI) State 0 0 0 0 0 0 150.40 15 0.50 28 0.75 30 0.44 30 0.59 43 0.85 45 0.44 45 0.65 60 0.90 600.42 60 0.69 75 0.91 120 0.37 75 0.71 90 0.93 180 0.34 105 0.73 120 0.93240 0.29 175 0.74 150 0.93 300 0.27 239 0.76 210 0.94 360 0.25 359 0.76270 0.95 390 0.22 479 0.76 390 0.95 1410 0.16 1395 0.58 506 0.96 15000.56 566 0.96 1745 0.49 1466 0.92 2920 0.33 1576 0.91 1816 0.89 29910.86

These experiments show that ferrate(VI) is not stable over long timeperiods; however, the stability and the half-life for decompositionimprove with higher ferrate yields. These experiments also exemplify theconcept of generating ferrate at a site proximal to the site of use suchthat the two sites are within a distance that allows for the ferrate totravel the distance within a half-life of its decomposition. In thisexample, the half-life of the ferrate in Experiments A and B isapproximately 400 min and 2250 min, respectively. The half-life offerrate in Experiment C is greater than 3000 min; however, theconsumption of Cl₂ and NaOH per unit weight of Fe(VI) is significantlygreater than that for Experiments A or B.

Example 5

Synthesis of Ferrate(VI) with Commodity Feeds

In this example, ferrate(VI) is synthesized with readily availablecommodity liquid bleach (13.4 wt % NaOCl), commodity liquid caustic(50.5 wt % NaOH), and 50 wt % ferric chloride in water solution.Initially 30.03 g of bleach solution is placed in a beaker containing aTEFLON®-coated magnetic stirring bar and the bleach beaker is cooled inan ice/water bath to about 15° C. Then 37.06 g of caustic solution isslowly added to the bleach with stirring such that the temperature ismaintained at about 15-20° C. The bleach/caustic solution is thentransferred to a jacketed reaction vessel. Then 2.97 g of 50% ferricchloride solution is injected into the bleach/caustic solution with asyringe needle positioned below the liquid level of the stirredbleach/caustic solution. The jacketed reaction vessel controltemperature is then set at 30° C., and sample aliquots (about 0.3 g) aretaken about every 30 minutes for Fe(VI) yield measurements according tothe procedure described in Example 2. In this case, the yield of ferratepeaked out at 68%.

Example 6

Synthesis of Ferrate(VI) with Commodity Feeds

Ferrate(VI) is synthesized utilizing the same liquid feed materials andmethodology as those used in Example 5, except 55.59 g of causticsolution is used instead of 37.06 g. In this case, the yield offerrate(VI) peaked out at 81%.

Example 7

Preparation of Ferrate(VI)

Ferrate is synthesized using the procedure of Example 1, except that 17g of chlorine was used instead of 6.5 g. 40 grams of coarse glass fritfiltered solution of hypochlorite in saturated sodium hydroxide solutionis added to a 50 mL Pyrex beaker with a TEFLON® stirring bar. The beakeris placed in a large crystallizing dish on a magnetic stirrer plate. Thecrystallizing dish has a water/ice mixture to maintain a temperature of19-20° C. Five grams of ferric nitrate nonahydrate is added over aperiod of four minutes to begin the experiment. The iron saltdistributes through the mixture but there is no visually apparentactivity for a few minutes. The temperature of the reaction mixtureslowly rises. About 10 minutes after the start of the iron addition, themixture turns dark purple. Simultaneously, the reaction temperaturepeaks at 31° C. At this point, a timer is started for the taking ofsamples for Ferrate(VI) analysis. The water/ice bath maintains aconstant temperature of 19-20° C.

Fraction Actual Re- Time, Actual Expected Observed of Iron action Temp-min Wt, g Absorbance Absorbance in (VI) State erature, ° C.  2 0.30 0.950.37 0.39 29  6 0.39 1.24 0.66 0.53 26 10 0.31 0.98 0.55 0.56 23 15 0.321.02 0.64 0.63 22 25 0.30 0.95 0.64 0.67 — 35 0.29 0.92 0.66 0.72 — 450.33 1.05 0.76 0.72 — 60 0.31 0.98 0.71 0.72 —

Example 8

Preparation of Ferrate(VI)

Ferrate is synthesized using the procedure of Example 1. 30 g of NaOHplus 75 g of water were mixed in the reaction chamber, followed by theaddition of 6.5 g of Cl₂. Another 70 g of NaOH is added. The solutionphase of this is reacted with 25 grams of ferric nitrate.

Exper- Temp, Caustic, Chlorine, C vs. Agita- iment ° C. 1st/2nd g IronForm B‡ tion 1 30 30/25 13 25/60 Fe/H₂O C T fitting 2 30 30/10 13 25/60Fe/H₂O C T fitting 3 30 30/0 10 25/60 Fe/H₂O C T fitting 4 35 30/0 1025/60 Fe/H₂O C T fitting 5 40 30/0 10 25/60 Fe/H₂O C T fitting 6 35 15/07.5 25/60 Fe/H₂O C T fitting 7 30 30/25 13 25/60 Fe/H₂O B Blade 8 3030/10 13 25/60 Fe/H₂O B Blade 9 30 30/0 10 25/60 Fe/H₂O B Blade 10 3530/0 10 25/60 Fe/H₂O B Blade 11 40 30/0 10 25/60 Fe/H₂O B Blade 12 3515/0 7.5 25/60 Fe/H₂O B Blade 13 30 30/25 13 25/60 Fe/H₂O C Passive 1430 30/10 13 25/60 Fe/H₂O C Passive 15 30 30/0 10 25/60 Fe/H₂O C Passive16 35 30/0 10 25/60 Fe/H₂O C Passive 17 40 30/0 10 25/60 Fe/H₂O CPassive 18 35 15/0 7.5 25/60 Fe/H₂O C Passive 19 30 30/25 13 25/60basepm* C Passive 20 30 30/10 13 25/60 basepm C Passive 21 30 30/0 1025/60 basepm C Passive 22 35 30/0 10 25/60 basepm C Passive 23 40 30/010 25/60 basepm C Passive 24 35 15/0 7.5 25/60 basepm C Passive 25 3530/0 10 25/30 sol 1† C Passive 26 35 30/0 10 25/30 sol 2 C Passive 27 3530/0 10 25/30 sol 3 C Passive 28 35 30/0 10 25/30 sol 4 C Passive 29 3530/0 10 25/30 sol 5 C Passive 30 35 30/0 10 25/30 sol 6 C Passive*Basepm means pre mix the iron solution with some of the NaOH in a shortloop before contacting the bleach. †Sol 1, 2, 3, 4, 5 and 6 means smallchelating molecule which might be needed to stabilize the iron withrespect to loss by precipitation as insoluble iron oxide. This approachmight also make it possible to reduce the amount of water in the recipe,this helps by concentrating all of the species to improve the kinetics.This may also cut down on forms of iron which are hostile to eitherferrate(VI) or bleach or both. ‡C vs. B means continuous vs. batch.

Example 9

Preparation of Ferrate(VI)

Ferrate is synthesized using the procedure of Example 1, except 12.9 gof chlorine was used instead of 6.5 g and the second addition of sodiumhydroxide was 25 g instead of 70 g. Reaction vessel is a 30 mL beaker ina 30° C. water bath. Begin with 15 g of hypochlorite/sodium hydroxidesolution. Over two minutes, add a proportionate amount of ferric nitratenonahydrate crystals (4.8 g). Begin pumping bleach into the vessel at arate of 1.2 g per minute. Simultaneously, continuously feed ironcrystals into the vessel at a rate of 0.24 g per minute. Stop after 20minutes, this point in time becomes time=0 in the table below. Duringthis period the maximum temperature was 40° C. but mostly a temperatureof close to 30° C. was maintained. After the additions were stoppedsamples were taken for spectrophotometric analysis.

Actual Fraction of Actual re- Time, weight, Expected Actual Iron in theaction temp- min gm absorbance absorbance (VI) state erature, ° C.  00.3267 2.93 1.121 0.38 30.1 10 0.3284 2.94 1.294 0.44 28.8 20 0.35503.18 1.466 0.46 28.2

Example 10

Literature Preparation of Ferrate(VI)

Ferrate was synthesized using a recipe given by Audette and Quail,Inorganic Chemistry 11(8) 1904 (1972).

IC 11(8) 1904 (1972) Experimental Procedure Recipe Weight, grams Weight,Experimental On a 75 grams Ingredient grams Moles Moles Procedure ofwater basis Water 75 10 75 1st NaOH 30 0.10 4 30 Cl₂ (gas) 6.5 0.0920.038 2.7 20.25 0.29 (75 g water basis) 2nd NaOH 70 0.24 9.6 72 Ferric25 0.062 0.005 2.02 15 Nitrate Nonahy- drate

Example 11

Procedure for the Synthesis of Ferrate(VI)

Take a small sample bottle and record its tare weight to the nearest0.01 grams. Inside a dry box, weigh 30 g of sodium hydroxide into a 300mL fleaker, 70 g of sodium hydroxide into a 150 mL fleaker, and 5.0 g offerric nitrate nonahydrate into the sample bottle. Cap each vessel. Takethe three vessels out of the dry box. Re-weigh and record the weight ofthe small sample bottle to the nearest 0.01 grams. Add 75 g of deionizedwater to the large fleaker. Re-cap the large fleaker and set it in ice.

Take the cap off the large fleaker, put a TEFLON coated stirring bar init, weigh it and record the weight. Set the fleaker in a largecrystallizing dish on a stirring plate, add ice to the crystallizingdish to above the level of the solution, and start the stirring. Put aglass thermometer in the solution.

Clean and dry the delivery tip from a chlorine delivery system. Startthe chlorine addition into the sodium hydroxide solution. Make sure thesodium hydroxide solution does not back up into the delivery tube towardthe chlorine cylinder. Watch for the speed of bubbles and don't go toofast. Watch the temperature and keep it below 20° C. Periodically checkthe weight of the fleaker plus contents and stop the chlorine additionwhen enough chlorine has been added (20 g of chlorine in this example).Record the weight of the fleaker plus contents.

Put the flask back in the ice bath with the thermometer. Slowly beginadding the second aliquot of NaOH. Watch the temperature closely; it ispreferably around 25° C. Filter the mixture through the fritted glassfilter. Put forty grams of filtrate in a 50 mL beaker with a shortstirring bar. Put the beaker in the crystallizing dish and add water andice or heat as necessary to establish the temperature at the set point.Put a thermocouple in the reaction vessel.

Begin adding ferric nitrate nonahydrate crystals from the small samplevial an simultaneously begin recording the temperature of the contentsof the reaction vessel. It will take four or five minutes to add theferric crystals. Once the purple color is strongly in evidence, begintaking samples for ferrate(VI) analysis.

Example 12

Preparation of Ferrate(VI)

Ferrate is synthesized using the procedure of Example 1, except 23.1 gof chlorine was used instead of 6.5 g. 40 g of coarse glass fritfiltered bleach in saturated sodium hydroxide solution was added to a 50mL Pyrex beaker with a TEFLON® stirring bar. The beaker was placed in alarge crystallizing dish on a magnetic stirrer plate. The water bathmaintained a temperature of 26-27° C. 5 g of ferric nitrate nonahydratewas added over a period of three minutes to begin the experiment*.During this step, the mixture foamed up slightly causing the ironnitrate crystals to tend to float on the foam and not mix in. At sixminutes the mixture was a dark purple color and sampling was initiatedby taking about 0.3 g and diluting to 100 g with cold buffer solution.Six minutes coincided with the peak mixture temperature, 42° C. Duringthe next few minutes, the foam continued to rise.

Actual Fraction of Actual Re- Time, Wt, Expected Observed Iron in actionTemp- min* gm Absorbance Absorbance (VI) State erature, ° C.  6 0.310.97 0.14 0.14 42  8 0.33 1.03 0.25 0.24 35 10 0.31 0.97 0.24 0.25 31 160.31 0.97 0.27 0.28 27.5 22 0.34 1.06 0.30 0.28 31 0.32 1.00 0.29 0.2946 0.32 1.00 0.30 0.29 *Timing began with the start of ferric nitratenonahydrate addition.

Example 13

Preparation of Ferrate(VI)

Ferrate is synthesized using the procedure of Example 1, except 12 g ofchlorine was used instead of 6.5 g. Reaction vessel is a jacketed beakermaintained at 35° C. Begin with 20 g of hypochlorite/sodium. Graduallyadd 1.6 g of ferric nitrate nonahydrate crystals. This is a 5 foldstoichiometric excess of hypochlorite over ferric(III). The maximumtemperature achieved during this step was 39° C.

Actual Fraction of Actual re- Time, weight, Expected Actual Iron in theaction temp- min gm absorbance absorbance (VI) state erature, ° C. 150.3233 1.36 0.86 0.63 35.2 30 0.3427 1.44 1.14 0.79 35.2 45 0.2984 1.261.10 0.87 35.2 60 0.3289 1.39 1.25 0.90 35.2

Example 14

Loop Reactor Procedure

A jacketed mixing vessel set to control the temperature at 30° C. isused. A reactor vessel in the form of a tube is used with a controlledtemperature setting of 35° C. A multi-head variable speed peristalticpump set to deliver sodium hypochlorite solution to the mixing chamberat a speed of approximately 30 mg/sec is used. Another tube on the pumphead is used to transfer mixture from the mixing chamber to the reactortube.

Prepare a sample vial with more than 10 g of ferric nitrate nonahydrate,record its weight. Prepare another sample vial with ferric nitratenonahydrate to deliver 3.42 g. Add 17.1 grams of sodium hypochloritesolution to the mixing chamber. Begin the mixing. Gradually add 3.42 gof ferric nitrate nonahydrate. Begin timing the experiment and begindelivering sodium hypochlorite solution from the peristaltic pump. Atone minute intervals, add 0.342 grams of crystals (measured visually)into the mixing chamber. After the 5 minute add, begin transferringreaction mixture to the loop by positioning the inlet of the peristalticpump transfer tube at the surface of the reaction mixture. After the 10,15 and 20 minute add, record the weight of the crystal vial. After the20 minute add, stop delivering sodium hypochlorite solution and stopadding crystals. Re-position the inlet to the peristaltic pump transfertube to near the bottom of the mixing vessel and continue pumping fromthere to the Loop reactor. When the Mixing Chamber is empty, stop theperistaltic pump. At 60 minutes, get a sample of the product from theoutlet end of the loop reactor and measure its absorbance. At 80minutes, get a sample of the product from the inlet end of the loopreactor and measure its absorbance.

Example 15

Preparation of Ferrate(VI)

Ferrate is synthesized using the procedure of Example 1. 40 g of coarseglass frit filtered bleach in saturated sodium hydroxide solution isadded to a 50 mL Pyrex beaker with a TEFLON® stirring bar. The beaker isplaced in a large crystallizing dish on a magnetic stirrer plate. Thecrystallizing dish has a water/ice mixture to maintain a temperature of19-20° C. 5 g of ferric nitrate nonahydrate is added over a period offour minutes to begin the experiment. The iron salt distributes throughthe mixture but there is no visually apparent activity for a fewminutes. The temperature of the reaction mixture does slowly elevate.Relatively suddenly, the mixture turns dark purple. This happened 10minutes after the start of the iron addition, simultaneously, thereaction temperature peaked at 31° C. At this point, a timer is startedfor the taking of samples for Ferrate(VI) analysis. The water/ice bathmaintained a constant temperature of 19-20° C.

Actual Fraction of Reaction Time, Actual Expected Observed Iron inTemperature, min Wt, gm Absorbance Absorbance (VI) State ° C.  2 0.300.95 0.37 0.39 29  6 0.39 1.24 0.66 0.53 26 10 0.31 0.98 0.55 0.56 23 150.32 1.02 0.64 0.63 22 25 0.30 0.95 0.64 0.67 — 35 0.29 0.92 0.66 0.72 —45 0.33 1.05 0.76 0.72 — 60 0.31 0.98 0.71 0.72 —

Example 16

Preparation of Ferrate(VI)

40 grams of coarse glass frit filtered bleach solution is added to a 50mL jacketed reaction vessel with a TEFLON® stirring bar. Controlledtemperature water is circulated through the jacket to control andestablish the reaction temperature. Five grams of ferric nitratenonahydrate is added over a period of a few minutes to begin theexperiment.

Time, Actual Expected Observed Fraction of Iron Actual Reaction min Wt,gm Absorbance Absorbance in (VI) State Temperature, ° C. Notes Tempcontrol point 30° C. 0 22.4 Begin iron addition 2 27 Complete ironaddition 2.5 30 3.5 33.9 Beginning of reaction noted 5 0.33 1.04 0.250.24 31.1 10 0.32 1.01 0.40 0.40 30.7 17 0.31 0.98 0.48 0.49 30.4 250.33 1.04 0.59 0.57 30.4 35 0.32 1.01 0.60 0.59 30.3 45 0.34 1.08 0.6950.64 30.5 Temp control point 35° C. 0 24 Begin iron addition 2 28.6Complete iron addition 2.5 32 3.5 37 Beginning of reaction noted 5 0.320.285 1.01 0.28 36 10 0.34 0.52 1.08 0.48 35.4 17 0.34 0.61 1.08 0.5635.3 25 0.34 0.67 1.08 0.62 35.3 35 0.31 0.68 0.98 0.69 35.3 45 0.340.813 1.08 0.75 35.3 60 0.43 1.11 1.36 0.82 35.2

Example 17

Preparation of Ferrate(VI)

Reaction vessel is a 30 mL beaker in a 30° C. water bath. Begin with 15g of hypochlorite/sodium hydroxide solution. Over two minutes, add astoichiometric amount of ferric nitrate nonahydrate crystals (3 g).Begin pumping bleach into the vessel at a rate of 1.2 g per minute.Simultaneously, continuously feed iron crystals into the vessel at arate of 0.24g per minute. Stop after 20 minutes, this point in timebecomes time=0 in the table below. During this period the maximumtemperature was 40° C. but mostly a temperature of close to 30° C. wasmaintained. After the additions were stopped samples were taken forspectrophotometric analysis.

Actual reaction Actual Expected Fraction of Iron in the temperature,Time, min weight, gm absorbance Actual absorbance (VI) state ° C.  00.3267 2.93 1.121 0.38 30.1 10 0.3284 2.94 1.294 0.44 28.8 20 0.35503.18 1.466 0.46 28.2

CONCLUSION

Thus, those of skill in the art will appreciate that the methods,devices, and uses herein provide a relatively easy and economical way ofproducing ferrate in close proximity to the site of use.

One skilled in the art will appreciate that these methods and devicesare and may be adapted to carry out the objects and obtain the ends andadvantages mentioned, as well as those inherent therein. The methods,procedures, and devices described herein are presently representative ofpreferred embodiments and are exemplary and are not intended aslimitations on the scope of the invention. Changes therein and otheruses will occur to those skilled in the art which are encompassed withinthe spirit of the invention and are defined by the scope of the claims.

It will be apparent to one skilled in the art that varying substitutionsand modifications may be made to the invention disclosed herein withoutdeparting from the scope and spirit of the invention.

Those skilled in the art recognize that the aspects and embodiments ofthe invention set forth herein may be practiced separate from each otheror in conjunction with each other. Therefore, combinations of separateembodiments are within the scope of the invention as claimed herein.

All patents and publications mentioned in the specification areindicative of the levels of those skilled in the art to which theinvention pertains. All patents and publications are herein incorporatedby reference to the same extent as if each individual publication wasspecifically and individually indicated to be incorporated by reference.

The invention illustratively described herein suitably may be practicedin the absence of any element or elements, limitation or limitationswhich is not specifically disclosed herein. Thus, for example, in eachinstance herein any of the terms “comprising”, “consisting essentiallyof” and “consisting of” may be replaced with either of the other twoterms. The terms and expressions which have been employed are used asterms of description and not of limitation, and there is no intentionthat in the use of such terms and expressions indicates the exclusion ofequivalents of the features shown and described or portions thereof. Itis recognized that various modifications are possible within the scopeof the invention claimed. Thus, it should be understood that althoughthe present invention has been specifically disclosed by preferredembodiments and optional features, modification and variation of theconcepts herein disclosed may be resorted to by those skilled in theart, and that such modifications and variations are considered to bewithin the scope of this invention as defined by the appended claims.

In addition, where features or aspects of the invention are described interms of Markush groups, those skilled in the art will recognize thatthe invention is also thereby described in terms of any individualmember or subgroup of members of the Markush group. For example, if X isdescribed as selected from the group consisting of bromine, chlorine,and iodine, claims for X being bromine and claims for X being bromineand chlorine are fully described.

Other embodiments are within the following claims.

What is claimed is:
 1. A method of continuously synthesizing ferrate, comprising: a) mixing an iron salt and an oxidizing agent in a mixing chamber to provide a mixture; b) delivering at least a portion of the mixture to a reaction chamber; c) continuously generating ferrate in the reaction chamber; d) delivering at least a portion of the ferrate to a site of use that is proximal to the reaction chamber; and e) adding additional iron salt and oxidizing agent to the mixing chamber; wherein said site of use is a site where said ferrate is contacted with an object it is to oxidize, disinfect, clean, plate, encapsulate, or coagulate or is utilized in organic synthesis.
 2. The method of claim 1, further comprising adding a base to the mixture.
 3. The method of claim 1, additionally comprising repeating steps (b) through (d).
 4. The method of claim 1, wherein said additional iron salt and oxidizing agent in step (e) is added in an amount to substantially replace the portion of the mixture delivered to the reaction chamber.
 5. The method of claim 2, wherein said base comprises an ion selected from the group consisting of a nitrogen base, the hydroxide ion, the oxide ion, the carbonate ion, and a combination thereof.
 6. The method of claim 2, wherein said base is sodium hydroxide.
 7. The method of claim 1, wherein said iron salt is selected from the group consisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate, ferrous sulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferrous hydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate, ferrous hydrogen carbonate, ferric carbonate, ferrous carbonate, and a combination thereof.
 8. The method of claim 1, wherein said iron salt is ferric chloride.
 9. The method of claim 1, wherein said oxidizing agent comprises at least one of the following: a hypohalite ion, a halite ion, a halate ion, a perhalate ion, ozone, potassium peroxymonopersulfate, potassium monopersulfate, halogen a peroxide, a peracid, a salt of a peracid, Caro's acid, and a combination thereof.
 10. The method of claim 1, wherein said oxidizing agent comprises sodium hypochlorite.
 11. A method of synthesizing ferrate, comprising: a) mixing an aqueous solution comprising an iron salt and an oxidizing agent in a mixing chamber to form a solution of ferrate; b) delivering at least a portion of the solution of ferrate to a site of use that is proximal to the mixing chamber; wherein said site of use is a site where said ferrate is contacted with an object it is to oxidize, disinfect, clean, plate, encapsulate, or coagulate or is utilized in organic synthesis.
 12. The method of claim 11, further comprising adding a base to the aqueous solution.
 13. The method of claim 12, wherein said base comprises an ion selected from the group consisting of a nitrogen base, the hydroxide ion, the oxide ion, the carbonate ion, and a combination thereof.
 14. The method of claim 11, wherein said iron salt is selected from the group consisting of ferric nitrate, ferrous nitrate, ferric chloride, ferrous chloride, ferric bromide, ferrous bromide, ferric sulfate, ferrous sulfate, ferric phosphate, ferrous phosphate, ferric hydroxide, ferrous hydroxide, ferric oxide, ferrous oxide, ferric hydrogen carbonate, ferrous hydrogen carbonate, ferric carbonate, ferrous carbonate, and a combination thereof.
 15. The method of claim 11, wherein said oxidizing agent comprises at least one of the following: a hypohalite ion, a halite ion, a halate ion, a perhalate ion, ozone, potassium peroxymonopersulfate, potassium monopersulfate, halogen, a peroxide, a peracid, a salt of a peracid, Caro's acid, and a combination thereof.
 16. The method of claim 11, further comprising adding additional iron salt and oxidizing agent to the mixing chamber in an amount to substantially replace the portion of the aqueous solution delivered to the site of use. 